There was a small migration of Acadians to the village (1759), after the British began the Expulsion of the Acadians from the Maritimes. Specifically, the Acadians migrated from present-day New Brunswick to avoid being killed or captured in the St. John River Campaign.
The town of Bécancour was created October 17, 1965, from an amalgamation of eleven municipalities. Bécancour was one of the province of Quebec's first amalgamated cities. At the time, Bécancour was the largest city in Quebec in terms of land area (as of 2003, the title belongs to La Tuque, Quebec).
Bécancour is now divided into six secteurs (lit. "sectors"): Bécancour, Saint-Grégoire, Gentilly, Précieux-Sang, Sainte-Angèle-de-Laval, and Sainte-Gertrude. Bécancour, Saint-Grégoire and Gentilly, each located near the shore of the Saint Lawrence River, can be considered the main urban centres. Autoroute 55 intersects Autoroute 30 and Route 132 at Saint-Grégoire.
Bécancour is part of the Trois-Rivières metropolitan area; many residents work in Trois-Rivières and commute across the Laviolette Bridge daily. The economy of Bécancour, once mainly agricultural, shifted towards heavy industry and manufacturing in the 1970s and 1980s. An industrial park was built in the area, attracting producers of aluminum, magnesium, refractory metals, and petroleum products; machine shops; and many related services, such as excavators and sales of industrial parts. A nuclear power plant, Gentilly Nuclear Generating Station, was commissioned in 1983 in the Gentilly sector; it was decommissioned in 2012.