Parenteau sought election as a borough councillor in Verdun's Desmarchais-Crawford division in the 2009 Montreal municipal election as a candidate of Vision Montreal. He was narrowly defeated by Ann Guy of the governing Union Montreal party. When he sought election as borough mayor in 2013, media reports described Parenteau as forty-two years old and the owner of an orthopedics supply store in Verdun.
Parenteau was narrowly elected as borough mayor of Verdun in the 2013 municipal election. The following March, after an internal investigation into the awarding of construction permits in the borough, he announced the dismissal of Verdun's chief public works director Pierre Boutin. Although Boutin was cleared by the investigation, Parenteau justified the dismissal on the grounds that "the link of trust between a mayor and his borough director is essential to work on any serious administrative reform." Parenteau subsequently said that preferential treatment and insider connections between developers and civil servants had cost taxpayers at least $1.5 million in lost profits. Parenteau arranged to remove about 1,500 tons of soil from an abandoned snow dump near the St. Lawrence River in April 2014, six months after it had been deposited and shortly after it was discovered to have been contaminated with creosote. Later in the same year, he advocated for the creation of a new beach in the same area, over suggestions from the oppositionProject Montreal party and others that the beach should be established near the Verdun Auditorium, closer to a MontrealMetro station. Parenteau eventually reversed his position in the face of public opposition and gave approval for the beach to be constructed near the auditorium. In early 2016, the Verdun borough announced that it would no longer lease a space for Réseau d'Entraide de Verdun , a food bank in the community. A representative of REV indicated that the borough had refused to meet with them to work out differences; Parenteau responded that this was not an accurate statement, and that the borough had made efforts to "mend fences" but ultimately ended the lease due to continued acrimony. Parenteau served as an associate member of the Montreal executive committee with responsibility for water, working in conjunction with Chantal Rouleau, the executive committee member responsible for this file. Parenteau was chosen as the third most popular politician in a 2016 YULorama poll of Montreal residents, behind Denis Coderre and Justin Trudeau. Parenteau was reelected in the 2017 municipal election as part of Équipe Denis Coderre. However, shortly after the election, he left the party to sit as an independent upon being named to the Montreal Executive Committee by Mayor Valérie Plante. He was named executive committee member in charge of citizen services and purchasing.
