Trinseo (TSE) DEFA14A Additional proxy soliciting materials

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

(Amendment No.     )

Filed by the Registrant  þ                              Filed by a Party other than the Registrant  ¨

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¨ Preliminary Proxy Statement

¨ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))

¨ Definitive Proxy Statement

þ Definitive Additional Materials

¨ Soliciting Material Pursuant to §240.14a-12

Trinseo S.A.

(Name of Registrant as Specified In Its Charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

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*** Exercise YourRight to Vote ***

Important Notice Regarding the Availability of Proxy Materials for the

Shareholder Meeting to Be Held on June 25, 2015.

	Meeting Information
	Meeting Type:	Annual General Meeting
TRINSEO S.A.	For holders as of:	April 17, 2015
	Date: June 25, 2015	Time: 1:00 p.m. CEST
	Location:   4 rue du Fort Niedergrünewald
	BP 512/Quartier Européen Nord    L-2015 Luxembourg   Grand Duchy of Luxembourg

	You are receiving this communication because you hold shares in the company named above.
TRINSEO S.A.   1000 CHESTERBROOK BLVD.   SUITE 3000   BERWYN, PA 19312	This is not a ballot. You cannot use this notice to vote these shares. This communication presents only an overview of the more complete proxy materials that are available to you on the Internet. You may view the proxy materials online atwww.proxyvote.comor easily request a paper copy (see reverse side).
	We encourage you to access and review all of the important information contained in the proxy materials before voting.

  See the reverse side of this notice to obtain   proxy materials and voting instructions.

Before You Vote  

How to Access the Proxy Materials

Proxy Materials Available to VIEW or RECEIVE:

NOTICE, PROXY STATEMENT AND ANNUAL REPORT ONFORM 10-K

How to View Online:

Have the information that is printed in the box marked by the arrow   (located on the following page) and visit: www.proxyvote.com.

How to Request and Receive a PAPER or E-MAIL Copy:

If you want to receive a paper or e-mail copy of these documents, you must request one. There is NO charge for requesting a copy. Please choose one of the following methods to make your request:

                              1)BY INTERNET:         www.proxyvote.com

                               2)BY TELEPHONE:     1-800-579-1639

                               3)BY E-MAIL*:             sendmaterial@proxyvote.com

*  If requesting materials by e-mail, please send a blank e-mail with the information that is printed in the box marked by the arrow     (located on the following page) in the subject line.

Requests, instructions and other inquiries sent to this e-mail address will NOT be forwarded to your investment advisor. Please make the request as instructed above on or before June 11, 2015 to facilitate timely delivery.

How To Vote  

Please Choose One of the Following Voting Methods

Vote In Person:Many shareholder meetings have attendance requirements including, but not limited to, the possession of an attendance ticket issued by the entity holding the meeting. Please check the meeting materials for any special requirements for meeting attendance. At the meeting, you will need to request a ballot to vote these shares.

Vote By Internet:To vote now by Internet, go towww.proxyvote.com.Have the information that is printed in the box marked by the arrow    (located on the following page) available and follow the instructions.

Vote By Mail:You can vote by mail by requesting a paper copy of the materials, which will include a proxy card.

M91818-P65397

Voting Items

The Board of Directors recommends you vote FOR the following proposals:

1. To elect the three Class I directors specifically named in the proxy statement, each for a term of three years.

2. To ratify the Board of Directors’ appointment of Donald T. Misheff, to fill a vacancy in Class III, with a remaining term of two years.

3. To approve, on an advisory basis, of the compensation paid by the Company to its named executive officers (the “say-on-pay vote”).

4. To approve, on an advisory basis, of the frequency of the say-on-pay vote in the future.

5. To approve the Company’s annual accounts prepared in accordance with accounting principles generally accepted in Luxembourg (“Luxembourg GAAP”) for the year ended December 31, 2014 (the “Luxembourg Annual Accounts”) and its consolidated financial statements prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”) including a footnote reconciliation of equity and net income to International Financial Reporting Standards (“IFRS”) for the year ended December 31, 2014 (the “Consolidated Accounts”) (together, the “Luxembourg Statutory Accounts”).

6. To resolve on the allocation of the results of the year ended December 31, 2014.

7. To approve the granting and discharge of the Company’s directors and auditor for the performance of their respective duties during the year ended December 31, 2014.

8. To ratify the appointment of PricewaterhouseCoopers Société cooperative (“PwC Luxembourg”) to be our independent auditors for all statutory accounts required under Luxembourg law for the year ending December 31, 2015.

9. To ratify the appointment of PricewaterhouseCoopers LLP (“PwC”) to be our independent registered accounting firm for the year ending December 31, 2015.

NOTE:Such other business as may properly come before the meeting or any adjournment thereof.