His parents, Georges Albert Tremblay, a notary, and Rollande Forest, had four boys: Michel, Gérald, Marcel, and François.

He worked at a consulting firm from 1977 to 1981, the Fédération des caisses d'entraide économique du Québec from 1981 to 1982, as well as various businesses in the hospitality and retail industry from 1982 to 1986 and the Société de développement industriel from 1986 to 1989.

He was also a member of the board of directors of the Caisse de dépôt et placement du Québec and Hydro-Québec, as well as the governor of the Quebec MBA Association.

He first sat in the National Assembly and served as Minister of Industry, Commerce, Science and Technology in the Bourassa Cabinet from October 11, 1989, to January 11, 1994, and in the Johnson Jr.

He was re-elected to the National Assembly in September 1994, and was named president of the Commission de l'économie et du travail from December 1, 1994, until his resignation on April 15, 1996.

He was also a successful entrepreneur, setting up a chain of specialty boutiques called Dans un Jardin which sold mostly perfume, but also jam, and other small delicacies.

Gérald Tremblay and his wife, Suzanne Tailleur, were married on November 24, 1979, and four years later adopted twins, Marie-Laurence and Georges-Etienne.

On November 6, 2005, Gérald Tremblay won his second term in office, easily winning against long-time rival Pierre Bourque by 74,646 votes.

He has been criticized by suburban mayors who decry his clear preference for Montreal to receive a much larger share of the island's tax revenues than it would have had the merger not taken place.

On October 30, 2012, a former Union Montreal party organizer alleged that Mayor Tremblay was involved in illegal financing with the mafia.