Atty. Jonathan Ptak
Jonathan Ptak is a partner in the firm’s class action group. His practice focuses on class proceedings, professional liability defence and commercial litigation.
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About Jonathan Ptak at a glance
Jonathan Ptak is a class action attorney, practicing at Koskie Minsky LLP. Recognitions include Best Lawyers in America — Class Action Litigation (2026).
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About
- Jonathan Ptak is a partner in the firm’s class action group
- His practice focuses on class proceedings, professional liability defence and commercial litigation
- He regularly appears before Courts at all levels in Ontario, including the Superior Court, Divisional Court and Court of Appeal
- Jon is recognized by Lexpert, Chambers Canada and Best Lawyers as a leading practitioner in class proceedings
- He has also been appointed to sit on the Ontario Class Action Bench-Bar Liaison Committee
- He has acted as counsel in a wide variety of class actions, involving product liability, medical implants, consumer protection, employment law (overtime class actions), public health (infectious disease outbreaks), securities misrepresentation, pension matters, Crown liability and other matters
- He is co-lead counsel in Heyder v
- Canada, in which a settlement was reached for $900 million involving alleged sexual misconduct in the Canadian Armed Forces and Department of National Defence
- It is one of the largest class action settlements in Canadian history
- He has been involved in many other of Canada’s largest settlements, including the settlement with Ernst & Young LLP in the Sino-Forest class action for $117 million, which is the largest settlement with an auditor in Canada
- He was lead counsel in Rosen v BMO, which was the first overtime misclassification case to be certified in Ontario (and not overturned on appeal), and was settled in 2016
- He is also lead counsel in Papassay v HMQ involving allegations about the Children’s Aid system and a historic failure to make claims on behalf of Crown Wards for abuse they have suffered
- He is part of a counsel team in a number of other leading class actions, including product liability actions about defective metal-on-metal hip implants, securities misrepresentation cases, and pension cases, among others
- In Jon’s professional liability defence practice, he has acted for lawyers, home inspectors, dentists, financial advisors and other professionals
- His commercial litigation practice includes complex commercial disputes, pension litigation as well as other matters such as employment
- A list of Jon’s current class action cases is appended below under the Experience tab
- Prior to joining Koskie Minsky in 2002, Jon practiced at a large international law firm
- He was also previously a caseworker and division leader at Downtown Legal Services (a community legal clinic) doing criminal defence work
- Jon obtained his Bachelor of Laws from the University of Toronto, where he won numerous mooting prizes
- He also spent a year abroad in Kuala Lumpur, Malaysia at a public health agency focusing on law reform
- Jon speaks and publishes regularly on issues related to class actions and commercial litigation
- He is a member of the Advocates Society and Ontario Bar Association
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Jonathan Ptak's Areas of Practice
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