The 2021 annual meeting2023 Annual Meeting of stockholders (the “Annual Meeting”) of A10 Networks, Inc., a Delaware corporation, will be held on Thursday,Wednesday, April 29, 202126, 2023 at 10:00 a.m. Pacific Time, at 2300 Orchard Parkway, San Jose, California, for the following purposes, as more fully described in the accompanying proxy statement:

Our board of directors has fixed the close of business on March 5, 2021February 28, 2023 as the record date for the Annual Meeting. Only stockholders of record on March 5, 2021February 28, 2023 are entitled to notice of and to vote at the Annual Meeting. Further information regarding voting rights and the matters to be voted upon is presented in the accompanying proxy statement. If you plan on attending the Annual Meeting as a stockholder, please follow the instructions on page 352 of the proxy statement.

Whether or not you plan to attend the Annual Meeting, we urge you to submit your vote via the Internet, telephone or mail.

We appreciate your continued support of A10 Networks, Inc. and look forward to either greeting you personally at the Annual Meeting or receiving your proxy.

This proxy statement and the form of proxy are furnished in connection with the solicitation of proxies by our board of directors for use at the 2021 annual meeting2023 Annual Meeting of stockholders of A10 Networks, Inc., a Delaware corporation (the “Company”), and any postponements, adjournments or continuations thereof (the “Annual Meeting”). The Annual Meeting will be held on Thursday,Wednesday, April 29, 202126, 2023 at 10:00 a.m. Pacific Time, at 2300 Orchard Parkway, San Jose, California. The Notice of Internet Availability of Proxy Materials (the “Notice”) containing instructions on how to access this proxy statement and our annual report is first being mailed on or about March 17, 202115, 2023 to all stockholders entitled to vote at the Annual Meeting.

The information provided in the “question and answer” format below is for your convenience only and is merely a summary of the information contained in this proxy statement. You should read this entire proxy statement carefully. Information contained on, or that can be accessed through, our website is not intended to be incorporated by reference into this proxy statement and references to our website address in this proxy statement are inactive textual references only.

Our business affairs are managed under the direction of our board of directors, which is currently composed of six members. On March 12, 2021, director J. Michael Dodson notified our board of directors that he would not stand for re-election atfive members and has the Annual Meeting. Following receipt of such notice, on March 15, 2021, our board of directors approved a decrease in the authorized number of directors to five, effective as of immediately following the end of Mr. Dodson’s term as a director, and as of immediately prior to the commencement of the Annual Meeting. Five of the sixcharacteristics:

The following table sets forth the names, ages and certain other information for each of our directors and director nominees as of March 17, 2021:15, 2023:

Our common stock is listed on the New York Stock Exchange. Under the listing standards of the New York Stock Exchange, independent directors must comprise a majority of a listed company’s board of directors. In addition, the listing standards of the New York Stock Exchange require that, subject to specified exceptions, each member of a listed company’s audit, compensation, and nominating and corporate governance committees be independent. Under the listing standards of the New York Stock Exchange, a director will only qualify as an “independent director” if, in the opinion of that listed company’s board of directors, that director does not have a relationship that would interfere with the exercise of independent judgment in carrying out the responsibilities of a director.

Audit committee members must also satisfy the independence criteria set forth in Rule 10A-3 under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), and the listing standards of the New York Stock Exchange. In addition, compensation committee members must also satisfy the independence criteria set forth under the listing standards of the New York Stock Exchange.

Our board of directors has undertaken a review of the independence of each director. Based on information provided by each director concerning his or her background, employment and affiliations, our board of directors has

Mr. Singer serves as our lead independent director. In this role, Mr. Singer presides over periodic meetings of our independent directors, serves as a liaison between our chairperson of the board of directors and the independent directors, and performs such additional duties as our board of directors may otherwise determine and delegate.

During our fiscal year ended December 31, 2020,2022, the board of directors held four (4)five (5) meetings (including regularly scheduled and special meetings) and acted by written consent ten (10)five (5) times. Throughout the year, directors met frequently to discuss our operations, the impact of Covid-19 on our business, strategic matters and other business. In many instances, these meetings resulted in formal board action approved by unanimous written consent. In other instances, these meetings resulted in our board of directors providing input to our management team throughout the year. No director attended fewer than 75% of the aggregate of (i) the total number of meetings of our board of directors held during the period for which he or she has been a director and (ii) the total number of meetings held by all committees of our board of directors on which he or she served during the periods that he or she served.

The compensation committee currently consists of Messrs. Braham, Chung, and Singer. Mr. Chung is the chair of the compensation committee. Our board of directors has determined that each member of this committee is independent under the applicable rules and regulations of the New York Stock Exchange and the SEC, a non-employee director, as defined pursuant to Rule 16b-3 promulgated under the Exchange Act, and an outside director, as defined under Section 162(m) of the Internal Revenue Code of 1986, as amended.

Messrs. Braham, Chung and Singer are the current members of our compensation committee. None of the members of our compensation committee is or has been one of our officers or employees. None of our executive officers currently serves, or in the past year has served, as a member of the compensation committee or director (or other board committee performing equivalent functions or, in the absence of any such committee, the entire board of directors) of any entity that has one or more executive officers serving on our compensation committee or our board of directors.

Our nominating and corporate governance committee uses a variety of methods for identifying and evaluating director nominees. In its evaluation of director candidates, our nominating and corporate governance committee will consider the current size and composition of our board of directors and the needs of our board of directors and the respective committees of our board of directors. Some of the qualifications that our nominating and corporate governance committee considers include, without limitation, issues of character, integrity, judgment, diversity (including, but not limited to, diversity of gender, ethnicity, race, international background and life experience), independence, area of expertise, corporate experience, length of service, potential conflicts of interest and other commitments. Nominees must also have the ability to offer advice and guidance to our Chief Executive Officer based on past experience in positions with a high degree of responsibility and be leaders in the companies or institutions with which they are affiliated. Director candidates must have sufficient time available in the judgment of our nominating and corporate governance committee to perform all board of director and committee responsibilities. Members of our board of directors are expected to prepare for, attend, and participate in all board of director and applicable committee meetings. Other than the foregoing, there are no stated minimum criteria for director nominees, although our nominating and corporate governance committee may also consider such other factors as it may deem, from time to time, are in our and our stockholders’ best interests.

If we hold the 20222024 annual meeting more than 30 days before or after the one-year anniversary of this year’s Annual Meeting, then our Secretary must receive the written nomination no earlier than the close of business on the 120th day before the actual date of the 20222024 annual meeting and no later than the close of business on the later of the following two dates:

Interested parties wishing to communicate with our board of directors or with an individual member or members of our board of directors may do so by writing to our board of directors or to the particular member or members of our board of directors, and mailing the correspondence to our General Counsel at A10 Networks, Inc., 2300 Orchard Parkway, San Jose, CA 95131, Attn: General Counsel. Each communication should set forth (i) the name and address of the stockholder, as it appears on our books, and if the shares of our common stock are held by a nominee, the name and address of the beneficial owner of such shares, and (ii) the number of shares of our common stock that are owned of record by the record holder and beneficially by the beneficial owner.

Our General Counsel, in consultation with appropriate members of our board of directors as necessary, will review all incoming communications and, if appropriate, forward such communications to the member or members of our board of directors to whom such communications were directed, or if none is specified, to the Chairperson of our board of directors.

Our board of directors believes that open communication between management and our board of directors is essential for effective risk management and oversight. Our board of directors meets with our Chief Executive Officer and other members of the senior management team at quarterly meetings of our board of directors, where, among other topics, they discuss strategy and risks facing the company, as well as at such other times as they deemed appropriate.

While our board of directors is ultimately responsible for risk oversight, our board committees assist our board of directors in fulfilling its oversight responsibilities in certain areas of risk. Our audit committee assists our board of directors in fulfilling its oversight responsibilities with respect to risk management in the areas of internal control over financial reporting, disclosure controls and procedures, and legal and regulatory compliance and cybersecurity, and discusses with management and the independent auditor guidelines and policies with respect to risk assessment and risk management. Our audit committee also reviews our major financial risk exposures and the steps management has taken to monitor and control these exposures. Our audit committee also monitors certain key risks on a regular basis throughout the fiscal year, such as risks associated with internal control over financial reporting and liquidity risk. Our nominating and corporate governance committee assists our board of directors in fulfilling its oversight responsibilities with respect to the management of risk associated with board organization, membership and structure, and corporate governance. Our compensation committee assesses risks created by the incentives inherent in our compensation policies. Finally, our full board of directors reviews strategic and operational risk in the context of reports from the management team, receives reports on all significant committee activities at each regular meeting, and evaluates the risks inherent in significant transactions.

Each non-employee director who first joins our board of directors will be granted an initial equity award with a value of $225,000. On the date of each annual meeting of stockholders, each continuing non-employee director will be granted an annual equity award with a value of $150,000. However, a continuing non-employee director who, as of the date of our annual stockholder meeting, has not served as a board member for the entire 12-month period prior

The following table provides information regarding the total compensation that was paid by the Company to each of our non-employee directors in 2020.2022. None of our non-employee directors were granted option awards in 2020.2022.

Our board of directors is currently composed of sixfive members. On March 12, 2021, director Michael J. Dodson notified our board of directors that he would not stand for re-election at the Annual Meeting. Following receipt of such notice, on March 15, 2021, our board of directors approved a decrease in the authorized number of directors to five, effective as of immediately following the end of Mr. Dodson’s term as a director, and as of immediately prior to the commencement of the Annual Meeting. At the Annual Meeting, each of the five recommended nominees, if elected, will serve for a one-year term. Each director’s term continues until the election and qualification of his or her successor, or such director’s earlier death, resignation, or removal.

As recommended by the nominating and corporate governance committee, the board’s nominees for election to the board are the following current members of the board: Tor R. Braham, Peter Y. Chung, Mary Dotz, Eric Singer, Dhrupad Trivedi and Dhrupad Trivedi.Dana Wolf. If elected, each nominee would hold office until the annual meeting to be held in 20222024 and until their successor is elected and qualified or until their earlier death, resignation or removal. For information concerning the nominee, please see the section titled “Board of Directors and Corporate Governance.”

If you are a stockholder of record and you sign your proxy card or vote by telephone or over the Internet but do not give instructions with respect to the voting of directors, your shares will be voted “FOR” the election of the nominees listed above. Each nominee has advised us that they are willing to serve on our board of directors, if elected; however, in the event that a director nominee is unable or declines to serve as a director at the time of the Annual Meeting, the proxies will be voted for any nominee who shall be designated by our board of directors to fill such vacancy. If you are a street name stockholder and you do not give voting instructions to your broker or nominee, your broker will leave your shares unvoted on this matter.

The election of each director requires a plurality vote of the shares of our common stock present in person or by proxy at the Annual Meeting and entitled to vote thereon to be approved. Broker non-votes will have no effect on this proposal.

The Dodd-Frank Wall Street Reform and Consumer Protection Act of 2010, or the Dodd-Frank Act, requires us to obtain an advisory vote (non-binding) from our stockholders on the compensation of our named executive officers as disclosed pursuant to Section 14A of the Exchange Act. This proposal, commonly known as a “Say-on-Pay” proposal, gives our stockholders the opportunity to express their views on our named executive officers’ compensation as a whole. This vote is not intended to address any specific item of compensation or any specific named executive officer, but rather the overall compensation of all of our named executive officers and the philosophy, policies and practices described in this proxy statement.

The Say-on-Pay vote is advisory, and therefore is not binding on us, the compensation committee or our board of directors. However, the Say-on-Pay vote will provide information to us regarding investor sentiment about our executive compensation philosophy, policies and practices, which the compensation committee will be able to consider when determining executive compensation for the remainder of the current fiscal year and beyond. Our board of directors and our compensation committee value the opinions of our stockholders and to the extent there is any significant vote against the named executive officer compensation as disclosed in this proxy statement, we will endeavor to communicate with stockholders to better understand the concerns that influenced the vote, consider our stockholders’ concerns and the compensation committee will evaluate whether any actions are necessary to address those concerns.

We believe that the information provided in the “Executive Compensation” section of this proxy statement, and in particular the information discussed in “Executive Compensation—Compensation Discussion and Analysis” beginning on page 2126 below, demonstrates that our executive compensation program was designed appropriately and is working to ensure management’s interests are aligned with our stockholders’ interests to support long-term value creation. Accordingly, we ask our stockholders to vote “FOR” the following resolution at the Annual Meeting:

“RESOLVED, that the stockholders approve, on an advisory basis, the compensation paid to the named executive officers, as disclosed in the proxy statement for the 20212023 Annual Meeting pursuant to Item 402 of Regulation S-K and other compensation disclosure rules of the SEC, including the compensation discussion and analysis, compensation tables and narrative discussion, and other related disclosure.”

The approval, on an advisory and non-binding basis, of the compensation of our named executive officers as described in this proxy statement requires the affirmative vote of a majority of the shares present in person or represented by proxy at the Annual Meeting and entitled to vote on this proposal. Abstentions are considered as a vote “against” the proposal because an abstention represents a share entitled to vote on this proposal. Broker non-votes will have no effect on the outcome of this proposal. You may vote “for,” “against” or abstain” on this proposal.

The audit committee of the board of directors has appointed Armanino LLP (“Armanino”), an independent registered public accounting firm, to audit our consolidated financial statements for our fiscal year ending December 31, 2021.2023. Armanino has served as our independent registered public accounting firm since September 2019 and audited our consolidated financial statements for our fiscal year ended December 31, 2019, 2020, 2021 and 2020.2022. Representatives of Armanino will be present at the Annual Meeting, and they will have an opportunity to make a statement and will be available to respond to appropriate questions from our stockholders.

At the Annual Meeting, our stockholders are being asked to ratify the appointment of Armanino as our independent registered public accounting firm for our fiscal year ending December 31, 2021.2023. The audit committee is submitting the appointment of Armanino to our stockholders because we value our stockholders’ views on our independent registered public accounting firm and as a matter of good corporate governance. If our stockholders do not ratify the appointment of Armanino, our board of directors may reconsider the appointment.

Notwithstanding the appointment of Armanino and even if our stockholders ratify the appointment, the audit committee, in its discretion, may appoint another independent registered public accounting firm at any time during our fiscal year if the audit committee believes that such a change would be in the best interests of the Company and its stockholders.

The following table presents fees for professional audit services and other services rendered to the Company by Armanino for our fiscal year ended December 31, 20202022 and 2019.2021.

In our fiscal year ended December 31, 2020,2022, there were no other professional services provided by Armanino, other than those listed above, that would have required the audit committee to consider their compatibility with maintaining the independence of Armanino.

The audit committee has established a policy governing our use of the services of our independent registered public accounting firm. Under the policy, the audit committee is required to pre-approve all audit and non-audit services performed by our independent registered public accounting firm in order to ensure that the provision of such services does not impair the public accountants’ independence. All fees paid to Armanino for our fiscal year ended December 31, 20202022 and 20192021 were pre-approved by the audit committee.

The ratification of the appointment of Armanino requires the affirmative vote of a majority of the shares of our common stock present in person or by proxy at the Annual Meeting and entitled to vote thereon. Abstentions will have the effect of a vote AGAINST the proposal and broker non-votes will have no effect.

The audit committee is a committee of the board of directors comprised solely of independent directors as required by the listing standards of the New York Stock Exchange and rules and regulations of the SEC. The audit committee operates under a written charter approved by the board of directors, which is available on our website at http://investors.a10networks.com. The composition of the audit committee, the attributes of its members and the responsibilities of the audit committee, as reflected in its charter, are intended to be in accordance with applicable requirements for corporate audit committees. The audit committee reviews and assesses the adequacy of its charter and the audit committee’s performance on an annual basis.

With respect to our financial reporting process, our management is responsible for (1) establishing and maintaining internal controls and (2) preparing our consolidated financial statements. Our independent registered public accounting firm is responsible for auditing these financial statements. It is the responsibility of the audit committee to oversee these activities. It is not the responsibility of the audit committee to prepare our financial statements. These are the fundamental responsibilities of management. In the performance of its oversight function, the audit committee has:

Based on the audit committee’s review and discussions with management and Armanino, the audit committee recommended to the board of directors that the audited financial statements be included in our Annual Report on Form 10-K for the fiscal year ended December 31, 20202022 for filing with the Securities and Exchange Commission.

This report of the audit committee is required by the SEC and, in accordance with the SEC’s rules, will not be deemed to be part of or incorporated by reference by any general statement incorporating by reference this proxy statement into any filing under the Securities Act of 1933, as amended (“Securities Act”), or under the Exchange Act, except to the extent that we specifically incorporate this information by reference, and will not otherwise be deemed “soliciting material” or “filed” under either the Securities Act or the Exchange Act.

The following table identifies certain information about our executive officers as of March 17, 2021.15, 2023. Officers are elected by our board of directors to hold office until their successors are elected and qualified. There are no family relationships among any of our directors or executive officers.

This Compensation Discussion and Analysis provides an overview of the material components of our executive compensation program. The following persons are collectively referred to in this Compensation Discussion and Analysis and the accompanying compensation tables as our “named executive officers”Named Executive Officers (“NEOs”):

Our products and services address networkingsecurity and securityinfrastructure technology requirements. Increasingly, A10 Networks, Inc. is positioned as a diversified, differentiated security solutions provider, structured to mitigate fluctuations from any single customer or region. While we are not immune from recessionary impacts, our industry leadership makes our offerings a priority over discretionary investments. We are well positioned to helpremain well-positioned for continued success with both enterprise and service provider customers. In 2022 we successfully navigated supply chain constraints, maintained robust gross margins and effectively managed our customers address the emerging themes of an increasingly complex cybersecurity landscapeoperating expenses, which drove profitability and new technology to support changing consumption trends.free cash flow. We have navigated challenges relatedrapidly adapted to fluctuations in the pandemicmacroeconomic environment and associated economic disruptions and have positioned A10 Networks, forInc. continues to be focused on consistent organic growth, increasing profitability, and increased profitability. Our business philosophy is to buildbuilding long-term value and we are committed to drive growth and improve profitability.value. Our executive compensation philosophy is focused on real pay delivery through revenue and operating margin growth that drives total shareholder return (“TSR”) and aligns employees with customers and stockholders.

Our 20202022 fiscal year was a year focused on driving growth and profitability with consistent operational excellence and execution amidst a challenging environment] and ourenvironment. Our compensation decisions were consistent with our financial performance, including the following:

We compensate for achievement of short-term and long-term financial and operating goals and have reasonable base salaries, limited perquisites, and no pensions or gross-up payments. Our executive compensation program is designed to attract and retain the best available personnel for positions of substantial responsibility, provide incentives for such persons to perform to the best of their abilities, and to promotereward our NEOs and other corporate officers for achieving strong operational performance and delivering on the Company’s strategic initiatives, both of which are important to the long-term success of our business.the Company. Our philosophy is underpinned by the following key principles:

The following sections describe each componentOur compensation committee is required to assess whether our compensation policies and practices and, in particular, our performance based compensation practices, encourage executives or other employees to take unnecessary or unreasonable risks that could threaten the long term value of the Company or that are reasonably likely to have a material adverse effect on the Company. Our compensation committee does not believe that our compensation policies and practices create risks that are reasonably likely to have a material adverse effect on the Company. Management believes that our practices adequately manage this risk because:

The charts below show the TDC of our Chief Executive Officer (“CEO”) and our other NEOs for fiscal 2022. These charts illustrate that a majority of executive compensation amountsis at-risk (85% for our CEO and awards were determinedan average of 70% for 2020.our other NEOs).

Base salary is the primary fixed component of our named executive officers’NEOs’ compensation. We use base salary to compensate our named executive officersNEOs for services rendered during the fiscal year and to ensure that we remain competitive in attracting and retaining executive talent. A named executive officer’sIn making base salary at hire is determined

Our compensation committee considered (i) the dates set forthdesired target total cash compensation opportunity and target total direct compensation opportunity that it believed were reasonable and appropriate for each executive officer, (ii) each executive officer’s prior annual cash incentive awards, (iii) our current business environment, (iv) the competitive market data, and (v) each executive officer’s past performance, anticipated future contributions, role, responsibilities, skills and experience when establishing their target award opportunities for 2022. Target award opportunities for our NEOs for fiscal 2022, prorated for the time served in the Bonus Plan.role, were as follows:

The compensation committee approved the grant to certain of our named executive officers of time-based restricted stock unit awards (“RSUs”) covering the following number of shares of our common stock and the grant ofbelieves that a significant emphasis on performance-based restricted stock unit awards (“PSUs”) enhance the pay-for-performance aspect of the compensation program and also further align the interests of executive management with our stockholders. Accordingly, on January 25, 2022, the compensation committee approved equity awards for certain of our NEOs with 70% of the target award value consisting of PSUs, and 30% of the award value consisting of RSUs covering the following target number of shares of our common stock:stock.

One-third (1/3rd) of the annual equity awardsshares of our common stock subject to each of the above-named executive officers and include both performance-based vesting and service-based vesting. The PSUsPSU award (the “Eligible Portion”) will become eligible to vest upon the achievement of certaineach of the three distinct stock price targets as set forth below (the “Performance Milestones”), as well as subject to continued service to the Company, with vesting of any portion for which the Performance Milestone is achieved (an “Eligible Portion”) to be scheduled to occurCompany. The Eligible Portion will vest in three equal installments, with the first one-third (1/3rd) of the Eligible Portion to vest within thirty (30) days of achievement of the Performance Milestone and an additional one-third (1/3) of the Eligible Portion to vest on each of the first and second anniversaries of achievement of the Performance Milestone, subject in each case to continued service on each such date.

The RSUs comprised the remaining 30% of the annual equity awards to each of the above-named executive officers and vest in three equal, annual installments with a first vest date of February 1, 2023, subject in each case to the named executive officer’s continued service through each vesting date. Upon

Mr. Weber’s PSU award includes both performance-based vesting and service-based vesting and will become eligible to vest upon the achievement of the $8.50 100-Day Stock Price, Mr. Becker’s PSUs are scheduled$18.00 or greater VWAP during the Performance Period (the “Weber Performance Milestone”), as well as continued service to vest as to one-half (1/2)the Company. The vesting of the PSUsshares of the Company’s common stock subject to the PSU Award will occur in three installments, with the first fifty percent (50%) of the shares of the Company’s common stock subject to the PSU Award to vest within thirty (30) days of achievement of the $8.50 100-Day Stock PriceWeber Performance Milestone and one-fourthan additional one-quarter (1/4) of the PSUs4th) to vest on each of the first and second anniversaries of achievement of the $8.50 100-Day Stock Price,Weber Performance Milestone, subject in each case to continued service on each such date. On the date of grant of the PSU award, the VWAP was $14.45. As of December 31, 2022, the Weber Performance Milestone has not been met.

Mr. Weber’s RSU is scheduled to vest in four equal, annual installments with a first vest date of July 5, 2023, subject in each case to Mr. Becker’sWeber’s continued service through each vesting date.

The vesting and performance objectives of the 2023 PSUs and RSUs are substantially similar in nature to the 2022 awards, with the exception that there are two stock price targets ($17.50 and $19.00) for the PSUs rather than the three targets established under the 2022 PSU awards and fifty percent (50%) of the shares of our common stock subject to the PSU award will become eligible to vest upon the achievement of each target in three installments with fifty percent (50%) within thirty (30) days of achievement of the applicable target and an additional one-quarter (1/4th) on each of the first (1st) and second (2nd) anniversaries of achievement of the applicable target, subject in each case to continued service on each such date.

The Company expects to Mr. Becker of 10,000 PSUsadopt a clawback policy regarding accounting restatements in accordance with the same termsSEC’s adoption of those grantednew rules to certainimplement Section 954 of the Dodd-Frank Wall Street Reform and Consumer Protection Act of 2010 once such final rule is implemented by the NYSE.

Pursuant to our Insider Trading Policy, all employees (including executives) are prohibited from engaging in transactions in publicly traded options and other derivative securities with respect to our common stock, including any hedging or similar transaction designed to decrease the risks associated with holding company securities. Our named executive officers aboveare also prohibited from pledging company securities as collateral or holding company securities in July 2020.a margin account.

The compensation committee has reviewed and discussed with management the section titled “Compensation Discussion and Analysis” above. Based on such review and discussion, the compensation committee recommended to the board of directors that the Compensation Discussion and Analysis be included in this proxy statement.

The following table provides information regarding the compensation paid to, or earned by, our named executive officers (each, an “NEO” and together, the “NEOs”) for each of our fiscal years ended December 31, 2020, 20192022, 2021 and 2018.2020.

The following table shows information regarding cash incentive and equity awards granted to our NEOs during our fiscal year ended December 31, 2020.2022.