Canadian troops do not see much action during the first two years of the Second World War, but in 1942 suffer more than 3000 casualties at the battle of Dieppe, a large-scale raid to test the German defences of the French coast. A small number of Canadian units are captured by the Japanese as part of the Hong Kong garrison, but Canadian forces see their heaviest fighting in Italy between 1943-45, and during the D-Day invasion on June 6, 1944 and the following campaign through eastern France. Canadian troops were largely responsible for the liberation of the Netherlands from German occupation between the autumn of 1944 and May 1945. Canadian naval and air forces also played important roles, and Canadian heavy industry expanded rapidly during the war to produce all kinds of military goods, including aircraft, ships, tanks, trucks and ammunition. More than 50,000 Canadians were killed in combat during the war.

Newfoundland, among one of Britain's oldest colonies, by a very narrow majority, votes to become part of Canada in 1949, becoming the tenth province to join confederation. However, Quebec nationalism entered a new phase after the 1950s, what is called The Quiet Revolution. French Canadians began to reject their feelings of inferiority in terms of English Canada, and also challenge the dominant position of the traditional Catholic church in Quebec society. Quebecois culture blossoms in writing, drama, music and visual arts. In Montreal, the world's second largest French-speaking city, French- language signs begin to appear, where signs had before been mostly only in English. The revolution stopped being so quiet with the appearance of the radical FLQ, a militant independence movement, which began a sporadic campaign of terrorism.

Massive immigration from war-ravaged Europe and a huge increase in births resulted in what is called the Baby Boom. This affected not just Canada, but much of the world was well. The Baby Boom includes people born from 1945 to the late 1950s.