He was a teacher from 1975 to 1978 at a secondary school in Montreal and a science and mathematics teacher at Collège Charles-Lemoyne between 1978 and 1985. He was a program coordinator for three years at the same college and was the general manager of the Académie Laurentienne located near Sainte-Adèle in the Laurentians.
Cousineau studied at the Université du Québec à Montréal and obtained a bachelor's degree in cellular and molecular biology. He also received a certificate in education at the same university.