Longtime mayor Jean Drapeau was re-elected to another four-year term in office, defeating Canadian federal parliamentarian Serge Joyal.
Source: Rodolphe Morissette, "Quatre nouveaux maires sur l'île de Montréal," Le Devoir, November 6, 1978, pp.
Source: "Les élections municipales," Le Devoir, 6 November 1978, A3.
Marcel Robidas of the Parti civique de Longueuil was re-elected as mayor, but nine of the seventeen council seats were won by the opposition Parti municipal de Longueuil.
Post-election changes: Source: Le Parti municipal de Longueuil: Les origines du Parti municipal Archived February 2, 2014, at the Wayback Machine, Société historique et culturelle du Marigot, accessed January 10, 2014.