Thomas DeVany Forrestall was born in Middleton Nova Scotia, in 1936. Forrestall's family later moved to Dartmouth which allowed him to attend Saturday morning art classes at the Nova Scotia College of Art in Halifax in the 1940s.
In 1954, Forrestall was awarded a scholarship to the Fine Arts department at Mount Allison University, where he studied with Lawren P. Harris and Alex Colville. He graduated in 1958 and received one of the first Canada Council grants for independent study which provided him with the opportunity to travel throughout Europe.
Upon returning to Canada he became the assistant curator of the Beaverbrook Art Gallery, while continuing as a freelance artist. He works primarily with water colours.
Forrestall’s art has been often classified as "Magic Realism". His work has been exhibited and represented in many major public collections internationally. His art has been reproduced in numerous histories of Canadian art and is featured in "High Realism in Canada" the 1974 book by Paul Duval. Two monographs on his paintings have been published, "Shaped by This Land" in 1974 and "Returning the Favour: Vision For Vision" in 1992.