Lack was born in 1946 in Montreal, Quebec, Canada, and gained a Bachelor of Arts in Psychology from McGill University in 1967, followed by a Master of Fine Arts in Sculpture at Universidad de Guanajuato, San Miguel de Allende, Mexico, in 1969. He lives and works in New York City, and is the father of Asher Lack, front-man of the band Ravens & Chimes.
The best-known films in which he featured are Scanners in 1981 and Dead Ringers in 1988, but he has also featured in cameo roles and independent films. Credits include Montreal Main (1974), The Rubber Gun (1978, which he also co-wrote with Allan Moyle, winning Genie Awards for both Performance and Screenplay), Head On (aka Deadly Passion, 1980); Perfect Strangers (1984), and All the Vermeers in New York (1990).
He was Artist in residence at Ancienne Manufacture Royale, Limoges, and Banff Institute of the Arts in 1988, Ford Motor Company, Dearborn, Michigan in 1989, and Connecticut College and Skidmore College in 1999. He received awards in the "Painting" category from the National Endowment for the Arts in 1987 and 1993, and the Canada Council for the Arts in 1991.