Joseph Saint-Amour was born in St. Jerome, Quebec, on 26 February 1852, to parents François-Xavier Payette dit Saint Amour and Mary Oumet. His father died at the age of 92. When he was just 10 years old, the young Joseph walked to Montreal to search for work, and became employed as a dishwasher at Hotel Dieu Hospital. As he began working at such a young age, he reportedly never learned to read or write. Later, he found work as a stonemason and contractor, and owned a farm on Lake Manitou. Later in life, he worked as a lifeguard at a beach – a job he held until he was 102. On 22 November 1872, he married Eugenie Letang, and would have 11 children with her – only 3 would outlive him. Eugenie died at the age of 90 in 1943, after over 70 years of marriage.

He was a frequent tobacco user, and smoked a pipe from the age of 12 until his death. Every morning after waking up, he would smoke his pipe before eating three to four raw eggs, which he would wash down with a tall glass of porter beer. In one week, he would reportedly eat five dozen raw eggs, 10 to 12 pounds of bananas, and 24 soft drinks as snacks in addition to his 3 main meals. Despite this diet, it was reported that he maintained a healthy weight throughout his entire life.

His hobbies included square dancing, listening to music, and watching wrestling and hockey on television. He also enjoyed watching the French-Canadian soap opera Les Belles Histoires des pays d’en haut. He owned a Ford Model T car, which he drove until he was 80.

Joseph Saint-Amour died in his home on 16 March 1962, just 18 days after his 110th birthday. He was survived by 3 children, 51 grandchildren, 124 great-grandchildren, and 23 great-great grandchildren.