In the 2005 Laval municipal election, Vaillancourt was re-elected with a large majority: 74.61% compared to 16% for his nearest opponent, Audrey Boisvert, an 18-year-old student.

[3] During the 2009 Laval municipal election, Vaillancourt was re-elected with a majority of 61.3%, compared to 22.64% for Lydia Aboulian, mayoral candidate for the Mouvement lavallois.

As part of the Commission of Inquiry on the Awarding and Management of Public Contracts in the Construction Industry(also known as the Charbonneau Commission), the Permanent Anti-Corruption Unit (French: Unité permanente anticorruption) inquired and searched Vaillancourt's residence for evidence of corruption, as well as Laval City Hall and two other administrative buildings on October 4, 2012.

Police from the Sûreté du Québec also raided more than ten safety deposit boxes rented by Vaillancourt at various financial institutions.

In the subsequent election to name his successor at Laval city hall, candidate Claire Le Bel went public on Radio Canada with a recording alleged to be that of Gilles Vaillancourt offering to fund her campaign with cash from questionable donors.