Born in Sainte-Anne-de-la-Pérade, Lower Canada, the son of Jean-Baptiste Garneau and Nathalie Rinfret dit Malouin, Garneau was the owner of a dry goods business.

He was president of the General Live Stock Breeders' Association and a member of the executive committee of the Dairy Men's Association from 1896 to 1905.

He was appointed to the Legislative Council of Quebec in 1901 for the Shawinigan division.

He was briefly the Minister of Agriculture in the cabinet of Simon-Napoléon Parent in March 1905.

He was made a Commander of the Order of St. Gregory the Great in 1916.