He studied law at Université Laval, was called to the Quebec bar in 1882[2] and began his legal practice in Montreal in 1883 before moving to Ottawa in 1884.

[2] He joined the law faculty at the University of Ottawa in 1891, and became proprietor of the newspaper Le Temps which supported the Liberal Party of Wilfrid Laurier.

He presided over the first Congress of Franco-Ontarians in 1910 called to oppose the Ontario government's attempts to suppress the use of the French language in schools.

He was also a leader in the struggle against Regulation 17 which was implemented by the provincial government in June 1912 to limit the use of French as a language of instruction in both the public and separate school systems.

In 1924, Belcourt was made Canada's Minister Plenipotentiary to the Interallied Conference in London[2] and, the next year, he presided over the meeting of the Inter-Parliamentary Union in Ottawa.