
From 1994 until his election as mayor in 2001, he was 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. He was also on the board of directors of several corporations.
In the 2001 election, Tremblay campaigned as the defender of towns and cities being forcibly merged into a new Island-wide city of Montreal, and received a great deal of support from opponents of the merger. However, in the subsequent referendum on the question of demerger, he was accused of betraying his supporters by coming out strongly in favour of the "no" side, supporting the megacity.
Since he took office, Tremblay has streamlined the city's operations but also generated controversy in some quarters. While his administration improved public consultation mechanisms, it is also considered by many to be one of the most secretive administrations in Montreal history, causing some to declare that the democratic deficit has grown during his tenure despite improvements to consultation. His administration also attempted a radical decentralization of the city by giving more power to the boroughs, but at the same time has come under attack 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 before the merger. However, many argue that these boroughs are even less responsive to the public than City Hall, since they are not required to offer public consultations on their decisions. Nevertheless, the public can (and sometimes does) force referendums on particular bylaw proposals.
Tremblay received criticism for his proposal to change the name of Avenue du Parc to Avenue Robert-Bourassa, in honour of former Quebec premier Robert Bourassa, without public consultation.
Tremblay generally keeps to himself, and is known for avoiding the media.
