The company was founded in 1955 as the Corporation de gaz naturel du Québec ("Natural Gas Corporation of Quebec"). Formal operations began in 1957, when the company acquired the gas operations that Hydro-Québec acquired with the 1944 takeover of Montreal Light, Heat & Power, an electric and gas utility. Following its acquisition, the company converted operations from a manufactured gas system to one that distributes natural gas.
The company would become Gaz Métropolitain in 1969.
In 1985, the company expanded its service area with the acquisitions of Gaz Inter-Cité Québec (serving eastern Quebec) and Gaz Provincial du Nord (serving the Abitibi-Témiscamingue region).
The company became a subsidiary of a new company called Noverco, in which the Caisse de dépôt et placement du Québec and Soquip were major investors. Later investors would include GDF Suez and Enbridge.
In 2003, the company shortened its name to its present name, Gaz Métro.
Quebec operations 
In September 2009, the number of employees was 1300. Number of customers in Quebec was some 180,000 customers. Its network in Quebec is nearly 10,000 kilometres (6,200 mi).
Vermont operations 
Gaz Métro owns Northern New England Energy Corporation, which in turn owns two utilities serving the US state of Vermont -- Vermont Gas, and Green Mountain Power (GMP).
According to management, GMP produces 5,000 short tons (4,500 t)-10,000 short tons (9,100 t) of CO2 annually, for which they are seeking offsets.
In 2008, GMP got 40% of its power from nuclear sources.
On July 12, 2011, Vermont's largest electric utility, Central Vermont Public Service (CVPS) agreed to be sold to Gaz Métro for $472.4 million. Pending approval by shareholders and regulatory authorities, CVPS operations will be merged with those of GMP making it the largest electric utility in the state with a total of 256,000 customers.
- "Gaz Métro veut acheter le deuxième distributeur du Vermont". Le Devoir (in French). June 23, 2006. Retrieved July 12, 2011.
- Burlington Free Press, June 15, 2009, page 8, Business Monday, "Vermont Gas recognized for customer service"
- Page, Candace (September 7, 2008). CREDITS:State could win in cap-and-trade deal. Burlington Free Press.
- Handelsman, Richard (December 1, 2008). My Turn:Truths, half-truths about energy. Burlington Free Press.
- "Vermont's biggest utility accepts buyout offer". Boston Globe. Associated Press. July 12, 2011. Retrieved July 12, 2011.