André Lespérance began his career as a lawyer at legal aid in 1983 where he practised criminal and youth law. In 1984, he joined the legal team at the Ministry of Revenu Québec in the department of fiscal law. Between 1985 and 1989, he obtained a Masters degree in Economic Sciences at the University of Montreal in order to work at the Bank of Canada thereafter as an economist. In 1989, he went to work as counsel in the office of the Attorney General of Canada. In 2008, he left the public service to join the law firm Lauzon Bélanger which then became Lauzon Bélanger Lespérance in 2010. On April 1st 2015, he officially joined the law firm Trudel Johnston & Lespérance.
During the past 20 years of his carreer, André Lespérance practiced in the fields of class actions and public law. He has acted as one of the lead counsels in the contaminated blood files, in the Gomery commission, the class action files against the banks (Marcotte and Laparé) and the class action files against the Canadian tobacco industry.