Lauren Tomasich

Lauren Tomasich

Partner, Litigation

Key Contact: Domestic and International Arbitration

Contact Information

tel: 416.862.6434



Lauren is a partner in the Osler litigation group and a key contact for the Domestic and International Arbitration Group. Her commercial litigation practice has a particular focus on commercial arbitration, corporate and securities litigation and white-collar defence and enforcement proceedings. Lauren is also a member of the Osler Risk Management and Crisis Response Group, and has acted on teams conducting internal investigations, as well as in managing cross-border regulatory investigations involving parallel class actions.

Lauren has significant experience with domestic and international arbitrations under a variety of procedural rules, including International Chamber of Commerce (ICC), London Court of International Arbitration (LCIA) and multiple ad hoc arbitrations. She has acted on numerous significant and highly confidential arbitrations in the construction, infrastructure, and mining and resource industries.

Lauren has a particular interest in leveraging arbitration procedure to have disputes adjudicated effectively with a view to strategic and business objectives. She designs bespoke dispute resolution provisions in commercial agreements to facilitate effective dispute resolution at the front-end of a deal, and crafts procedural rules in ad hoc arbitrations to deal with unique circumstances. For example, she has acted on matters where she has designed and negotiated unique arbitration procedures, including a highly confidential dispute arising from a private M&A transaction and an emergency arbitration for an online technology learning company. She is also very active in the arbitration community, sitting as the Chair of the Advocates’ Society Arbitration and Mediation practice group, on the board of the ADR Institute of Canada (ADRIC) and is a member of the ICC Canada Arbitration Committee.

Lauren’s corporate and securities litigation practice involves expedited hearings before the Ontario Securities Commission, oppression claims and shareholder disputes. She also works closely with Osler’s Emerging and High Growth Companies group to provide advice to early stage and technology companies, and brings a business-minded view to efficient and effective dispute resolution and risk management at critical stages of companies’ growth.

Lauren has also represented various companies facing class actions in a variety of circumstances, including privacy and data breaches, claims of environmental property damages, securities, product liability and pensions and benefits. She has experience at all stages of a class proceeding, including certification motions, various procedural motions, a large common issues trial and appeal, and costs proceedings.

Lauren has appeared at all levels of court in Ontario, and has spent some time with Osler’s Calgary office, during which time she appeared before the Alberta courts. Lauren was previously seconded to the OSC, during which time she participated in a criminal insider trading trial.

In 2022 Lauren was recognized by Lexpert as one of Canada’s Rising Stars: Canada’s Leading Lawyers Under 40. The Lexpert Rising Stars awards recognize private practice and in-house lawyers who are emerging leaders in the Canadian legal community. Winners are selected by a distinguished advisory board, which considers the contributions that nominees make to their firm, company or department, as well as to the profession and larger community.

    • GitHub Inc. in its class proceeding concerning an alleged data breach involving the information of credit card applicants
    • A multinational social media company in a privacy class actions in British Columbia, arising out of interactions with Apple's operating systems
    • A IT service management company in a privacy class action resulting from a large data breach involving personal information belonging to credit card applicants
    • Vale (Inco) Limited in a class action trial, and the successful appeal of the trial decision (leave to appeal to the Supreme Court of Canada denied). Lauren also acted on various motions before, during and after the common issues trial including a decertification motion, a motion to disqualify one of the plaintiff’s expert witnesses, and a motion to amend the common issues subsequent to the close of trial
    • A large international mining company in an ad hoc arbitration in respect of various claims arising from the construction of a large-scale mineral processing facility
    • A large pharmaceutical company in an investigation by the Autorité des marches financiers with related investigations by US authorities
    • The Canada Mortgage and Housing Corporation in class proceedings dealing with pension surplus and plan amendments, involving complex procedural issues
    • A large North American industrial chemical and services supplier in a confidential, international ad hoc arbitration in respect of a commercial dispute
    • Magna International Inc. in opposing the application before the Ontario Securities Commission, brought by Staff of the OSC and intervening institutional shareholders in opposition to the company’s dual-class share capital reorganization
    • Merrill Lynch Canada in a proposed class action alleging mismanagement of client accounts
    • General Motors of Canada Inc. in class proceedings brought on behalf of a group of former employees in respect of their entitlement to pension benefits following their change of employment
    • A large global manufacturer of water treatment facilities in a complex multi-jurisdictional product liability case involving many parties
    • A CEO of a Canadian energy company in a joint investigation by the US Securities Exchange Commission and the Alberta Securities Commission, and related class proceedings
    • An online educational service provider in a confidential emergency ad hoc arbitration pertaining to a potential business critical service outage
    • An International Client a dispute between joint venture partners under the London Court of International Arbitration (LCIA)

  • Chambers Canada: Canada’s Leading Lawyers for Business: Recognized in Dispute Resolution: Arbitration
  • Benchmark Litigation Canada: Recognized in Dispute Resolution (40 & Under Hot List; Future Star)
  • The Canadian Legal Lexpert Directory: Recognized in Commercial Arbitration; Litigation – Corporate Commercial; Litigation – Securities
  • Lexpert Rising Stars: Recognized as a Rising Star

  • Law Help Ontario, Pro Bono Law Ontario, Duty Counsel Volunteer

  • Canadian Bar Association
  • Ontario Bar Association
  • Law Society of Ontario
  • The Advocates’ Society (Arbitration and Mediation Practice Group Chair)
  • ADR Institute of Canada (ADRIC) Board member
  • American Bar Association
  • Young Canadian Arbitration Practitioners (YCAP)
  • Women’s White Collar Defense Association – Toronto Chapter Secretary
  • ROAP Americas, Delos Advanced Oral Advocacy Training Program in International Arbitration (Faculty)