Sandra Mastrogiuseppe

Sandra is a seasoned litigator with 30 years of experience in commercial litigation and arbitration. 

Sandra has been involved in a broad range of high-stakes files, including contractual conflicts, injunctions, seizures and shareholder disputes.

As part of her shareholder disputes practice, Sandra represents individuals, corporations, business owners and shareholders—notably those of private and family-owned companies—before the Courts in complex oppression remedy proceedings, across a broad range of industries. Known for her thoughtful and comprehensive analysis of complex disputes, she develops practical, strategic solutions tailored to her clients’ objectives. She is also highly effective in negotiating viable alternatives or favourable resolutions where appropriate. 

Her practice also includes personal injury and medical malpractice litigation, representing individuals and their families in complex matters to pursue the best possible outcomes on their behalf. 

Sandra has been consistently recognized in The Best Lawyers in Canada® as a leading lawyer in the areas of Alternative Dispute Resolution and Corporate & Commercial Litigation.

She has also been consistently recognized in the Canadian Legal Lexpert Directory in Corporate Commercial litigation.

Represented BCE Inc. and Bell Canada before the Superior Court (2008 QCCS 907) in a landmark commercial case approving BCE’s proposed plan of arrangement in the context of a $51.7 billion privatization. This decision, while dismissed by the Quebec Court of Appeal, was ultimately confirmed by the Supreme Court of Canada, (2008 SCC 69) thereby setting the standard for oppression claims across Canada. 

Represented Simms Sigal & Co. Ltd. in Costco Wholesale Canada Ltd. v. Simms Sigal & Co. Ltd., one of the highest punitive damages awards ($500,000) upheld by the Quebec Court of Appeal (2020 QCCA 1331; 2017 QCCS 5058) in a private commercial dispute involving claims of contractual interference and reputational harm.

Represented 555 Carriere Holdings Inc. before the Quebec Court of Appeal in Canada (Attorney General) v. 555 Carriere Holdings Inc. (2018 QCCA 2215; 2018 QCCS 565), a leading commercial real estate decision clarifying the enforceability of options to purchase contained in commercial leases. The Court confirmed that an unexercised option to purchase is a personal contractual right that does not bind a subsequent purchaser solely by virtue of the publication of the lease, thereby providing important guidance on the distinction between personal and real rights under Quebec civil law. 

Successfully represented a significant number of Montreal’s most successful and accomplished business owners, family-owned enterprises, business leaders and private shareholders across a variety of sectors in high-stakes shareholder disputes and corporate governance conflicts. 

These mandates included significant contested proceedings before the Courts, as well as the confidential resolution of sensitive disputes through strategic negotiation.

Sandra has been a guest lecturer at the Faculty of Law of McGill and spoken at a number of professional legal conferences, including one recently organized by the Canadian Bar Association:  Peut-on prévenir les recours en oppression et litiges entre actionnaires? (April, 2026)