About Tannahill, Lockhart & Clark Law LLP

Tannahill, Lockhart & Clark Law LLP is a general practice law firm in Mississauga that has served Peel Region, including Mississauga, Brampton, and Caledon, since 1978. Founding partners Douglas Tannahill and John Lockhart met while working together at another Brampton firm, West & Robb, and became partners that year. Tannahill was called to the bar in 1975 and focuses on corporate and commercial work, including commercial real estate and leasing. Lockhart was called to the bar in 1977 and built a practice in general litigation, estate litigation, wills, and real estate.

John Lockhart's son, Timothy Lockhart, joined the firm and was called to the bar in 2013. Tim practices civil and estate litigation along with real estate and wills work, and the team describes its combined legal experience as nearly 150 years. Today the firm is a general practice with a particular focus on estate litigation, handling wills and estates, civil litigation, real estate, and business law for individuals and businesses across Peel Region.

In the community

  • John Lockhart holds executive responsibilities with the Christian Legal Fellowship.
  • John Lockhart has been involved with the Calcutta Mission of Mercy, the Brampton Life Centre, and Kennedy Road Tabernacle.
  • Douglas Tannahill has supported several benevolent organizations in Brampton, including a local homeless shelter.
  • Timothy Lockhart is a member of the Rotary Club of Brampton and served six years on its board of directors.

Good to know

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Fees & payment

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This firm’s lawyers at a glance

Called to the bar
1977 · median 49 years in practice 1 of 3 lawyers

Where to find them

5805 Whittle Rd, Unit 10, Mississauga, ON L4Z 2J1 · 905-502-5770

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This listing was generated by AI from public sources in September 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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