 Hartt was born in Montreal, Quebec to Maurice Hartt, a Quebec MNA and MP, and brother of the late Joel Hartt (1940–2009).He received a Bachelor of Arts degree in 1958, a Master of Arts degree in 1961, and a Bachelor of Civil Law degree in 1963 from McGill University.He was called to the Quebec Bar in 1965 and created a Queen's Counsel in 1984.