The appointment was confirmed Wednesday at the PQ government's cabinet meeting in Quebec City.
"I have a lot of confidence in Nicolas Girard's abilities," Transport Minister Sylvain Gaudreault said.
Girard will succeed Paul Côté at the helm of the agency. Côté was running the AMT on a interim basis until a new permanent president could be appointed.
Girard lost his seat in the Montreal riding of Gouin to Québec Solidaire co-spokesperson Françoise David. She defeated him by 4,564 votes in the Sept. 4 election.
Coalition Avenir Québec Leader François Legault denounced the appointment as cronyism.
"Mr. Girard, with all his skills, doesn't have any experience in management. So this is exactly what the Parti Québécois had been denouncing: partisanship over ability," Legault said.
The presidency of the AMT carries a salary of about $170,000 a year, well more than the basic MNA salary of $86,242 plus certain expenses.