Finlayson earned her B.A. (Biology) from the University of Toronto in 1936, certification in Taxonomy and Biological Control by ARPE in 1971 and an LLD from Simon Fraser University in 1996.

Thelma Finlayson began her entomological career in 1937 as a Technical Officer for the Canada Dept. of Agriculture, Belleville Research Institute.  She was one of the first women scientists to enter the federal research branch. In 1967, Finlayson was appointed Assistant Professor and Curator of Entomology at Simon Fraser University—the first woman in the Department of Biological Sciences.  She was a founding member of SFU’s Centre for Pest Management, rose to the position of Full Professor (1976), and has held the position of Professor Emerita since 1979 (SFU’s first Professor Emerita). Finlayson’s primary interest is in the taxonomy of natural enemies of insects with particular application to Biological Control.  She published approximately 40 papers, Memoirs and book chapters during her career, and was internationally recognised for her work on the taxonomy of immature Hymenoptera.

In 1983, Finlayson was appointed as Special Advisor at the SFU Academic Advice Centre—now the Thelma Finlayson Centre for Student Engagement—and retained that position until 2012 (during which time she advised more than 8,000 students).  In addition to the tremendous amount of time that she devoted to students, Thelma was a clear advocate of entomology through significant financial contributions, including an endowment to establish the Finlayson Chair in Biological Control, and entrance scholarships and fellowships for students in the Master of Pest Management program.

Professor Finlayson was named to the Order of Canada in 2005 as “a trailblazing entomologist and a beloved teacher and advisor” and has received many other honours including being elected a Fellow (1993) and Honorary (1990) Member of the Entomological Society of Canada, Honorary Member of the Entomological Societies of both BC (1985) and Ontario (2013) and made a lifetime Member of the Canadian Universities Women's Society.