About Kostyniuk & Greenside Lawyers

Kostyniuk & Greenside is a Toronto firm that focuses on insurance law, based on Dundas Street West in the city's Etobicoke area. It has provided legal services to insurers, brokers, independent adjusters, corporations and individuals in the insurance field for approximately 40 years. Its litigation practice covers personal injury, statutory accident benefits disputes before the Licence Appeal Tribunal, insurance coverage disputes, loss transfer and subrogation claims, long-term disability insurance claims, product liability, class actions and commercial disputes, along with corporate transactions and administrative law work.

The firm takes its name from two lawyers. Nestor E. Kostyniuk, a partner, was called to the Ontario Bar in 1979, became a Certified Specialist in Civil Litigation in 1992, and has concentrated in insurance law ever since. Derek R.J. Greenside was called to the Bar in 1987, became a Certified Specialist in Civil Litigation in 1999, and is now retired from active practice. Today the team runs to about twenty lawyers, and the firm points to its history as trial lawyers as part of why many of its current lawyers first joined as articling students before staying on as associates or partners.

In the community

  • A partner at the firm serves on the Board of the Toronto Lawyers Association and represents it on the Roundtable of Legal Diversity Associations (RODA).
  • In 2015, a partner at the firm founded a pro bono initiative in the United Kingdom that continues to operate today through a law school there.
  • During law school, an associate at the firm volunteered with Pro Bono Students Canada, focusing on human rights advocacy for adults with disabilities.

Certified Specialists

A designation granted by the Law Society of Ontario, not a self-declared area of focus.

This firm’s lawyers at a glance

Called to the bar
2014–2026 · median 2 years in practice 7 of 21 lawyers
Law schools
Kent University of Law, Ottawa University, University of New Brunswick 3 of 21 lawyers
Languages on the roster
English, French

Where to find them

5468 Dundas Street W., Suite 300, Toronto, Ontario, M9B 6E3 · 416-762-8238

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This listing was generated by AI from public sources in August 2026. It may contain errors, and we can’t guarantee it’s accurate or complete. Before you rely on anything here, verify it on the firm’s own website. Verify licence status in the Law Society of Ontario directory ↗

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