Anthony O’Brien

Anthony O’Brien is a partner in the Toronto office of Siskinds LLP. His practice focuses on representing retail and institutional investors in securities class actions and other shareholder rights litigation. He has experience prosecuting securities class actions in the courts of Ontario, British Columbia and Québec.

Anthony has been class counsel in securities class actions that have collectively recovered hundreds of millions of dollars for investors, including SNC-Lavalin Group ($110 million), TD Asset Management ($70.25 million), Canadian Imperial Bank of Commerce ($26 million), Agnico-Eagle Mines ($17 million), Smart Technologies (US$15.25 million), Tahoe Resources (US$13.5 million), Canadian Solar (US$13 million), Baffinland Iron Mines ($6.5 million) and Donnybrook Energy/Donnycreek Energy ($5.5 million).

Anthony has been recognized in The Best Lawyers in Canada™ and the Canadian Legal Lexpert Directory for class actions, and has been included in the 500 Global Plaintiff Lawyers guide by Lawdragon.

Anthony brings a unique international perspective to his class action practice, having previously worked with Australia’s pre-eminent plaintiff class action law firm. While there, he was involved in a securities class action against an Australian insurer that resulted in a settlement of A$132.5 million for the class. Prior to joining Siskinds, he also worked in the corporate and securities department of one of Canada’s leading law firms.

Anthony is a supervising lawyer for the Osgoode Hall Law School’s Investor Protection Clinic, which provides pro bono legal services to individuals who have suffered investment losses.

During law school, Anthony was Editor of the Melbourne University Law Review.

• Member, The Advocates’ Society
• Chair, Securities Litigation Practice Group, The Advocates’ Society (2025–2026)
• Cross Border Legal Network

• The Best Lawyers in Canada™, Class Action Litigation, 2024–2026
• Canadian Legal Lexpert Directory, Class Actions
• Lawdragon, 500 Global Plaintiff Lawyers, 2024–2025

Anthony’s representative matters include:

• Mutual fund trailing commission class actions: Counsel to the class in ongoing class actions seeking recovery for unitholders against mutual fund managers and trustees relating to trailing commissions paid to discount brokers on mutual funds held by those unitholders.
• Trustees v SNC-Lavalin Group: Counsel to the class in this secondary market securities class action against a TSX-listed global engineering and construction company, which resulted in a settlement of $110 million for the class.
• Abdula v Canadian Solar: Counsel to the class in this secondary market securities class action against a NASDAQ-listed solar company, which resulted in a settlement of US$13 million for the class. It involved a precedent-setting decision of the Ontario Court of Appeal clarifying that issuers listed on stock exchanges outside Canada can be sued under the secondary market liability regime in the Ontario Securities Act.
• Rooney v. ArcelorMittal: Counsel to the class in this securities class action relating to the take-over of a TSX-listed mining company, which resulted in a settlement of $6.5 million for the class.
• AFA v Agnico-Eagle Mines: Counsel to the class in this secondary market securities class action against a TSX-listed mining company, which resulted in a settlement of $17 million for the class.
• Tucci v Smart Technologies: Counsel to the class in this securities class action relating to the initial public offering of a technology company, which resulted in a settlement of US$15.25 million for the class.

Anthony has spoken at numerous conferences, and authored a number of articles, addressing class action and securities law issues, including the following:

• Chair, 15th Annual Securities Symposium, The Advocates’ Society, September 19, 2025
• Moderator, “Update on Securities Class Actions: Practice and Recent Cases”, 14th Annual Securities Symposium, The Advocates’ Society, September 19, 2024
• Speaker, “Securities Issue Spotting with Securities Practitioners”, Securities Litigation from A to Z, The Advocates’ Society, April 12, 2024
• Speaker, “Do’s, Don’ts and Practical Tips for Using Financial Statements in Litigation”, Advocacy Hour: Working with Financial Statements, The Advocates’ Society, March 28, 2024
• Moderator, “Governing Emerging ESG Risks and Liabilities” and “Recent Developments in Securities Class Actions”, 13th Annual Securities Symposium, The Advocates’ Society, September 28, 2023
• Speaker, “Legislative Changes Across the Nation”, 12th Annual Class Actions Colloquium, Ontario Bar Association, December 2, 2020
• Speaker, “Overview of Class Proceedings”, Fundamentals of Class Actions Law, Ontario Bar Association, November 26, 2020
• Speaker, “Current Issues in Securities Class Actions”, 10th Annual Securities Symposium, The Advocates’ Society, September 9, 2020
• “Class Action Counsel Fees: A Fair and Reasonable Approach” (April 2011) (co-author)
• “Third-Party Funding for Class Actions, and Control over the Litigation” (2014) 55 Canadian Business Law Journal 165 (co-author)
• “Canada” (Chapter 9), Shareholder Claims (UK: Jordan Publishing Limited, 2012) (co-author)

August 6, 2014 /CNW/ - Siskinds LLP, one of Canada's leading class action law firms, is pleased to announce that it has been named again as the top-ranked Canadian firm in the "SCAS 50." Siskinds ranked 16th overall in the a global ranking of the world's 50 leading securities class action law firms, the highest ranking ever attained by a Canadian firm. It is compiled annually by Securities Class Action Services, a unit of Institutional Shareholder Services (ISS). Siskinds was the first Canadian firm to rank in the top 50 and has been the top Canadian firm each year since 2010.

• Divisional Court denies leave to appeal in Trailing Commission class action
• Recent Developments in Securities Class Actions: Pre-Certification Jurisdictional Challenges
• A good day for do-it-yourself investors: The CSA proposes to prohibit the payment of trailing commissions to discount brokers
• Towards a More Cooperative Canadian Class Action Regime: CBA Adopts Revised Judicial Protocol on Multijurisdictional Class Actions
• The Supreme Court of Canada Provides Guidance on Preferable Procedure and Access to Justice