<Page> EXHIBIT 5.3 Barristers & Solicitors McCarthy Tetrault LLP Patent & Trade-mark Agents P.O. Box 10424, Pacific Centre Suite 1300, 777 Dunsmuir Street McCarthy Tetrault Vancouver BC V7Y 1K2 Canada Telephone: 604 643-7100 Facsimile: 604 643-7900 www.mccarthy.ca November 10, 2003 TO: United States Securities and Exchange Commission RE: Public Offering of Common Shares We refer to the Registration Statement on Form F-10 and related prospectus (the "Prospectus") of Sierra Wireless, Inc. (the "Corporation") dated as of November 10, 2003 for the registration of Common Shares of the Corporation. We hereby consent to being named in the Prospectus as counsel to the underwriters as defined in the Prospectus, with respect to Canadian law under the heading "Legal Matters". Yours truly, "MCCARTHY TETRAULT LLP" Vancouver, Calgary, London, Toronto, Ottawa, Montreal, Quebec, New York and London, England An Ontario Limited Liability Partnership