Bryson Carlyle Donnan was born in St. Catharines, Ontario, the son of Samuel Donnan and Elizabeth (née Bryson) on 31 March 1895. He signed up to serve in the Canadian Expeditionary Force in September 1914, when he was working as a schoolteacher. He was commissioned a lieutenant at the Battle of the Somme. He became a barrister in 1920 and was the senior partner in the law firm of Donnan and Butler, becoming a King's Counsel in 1933 and Crown Attorney for Hastings County.
Donnan continued his association with the military, becoming a lieutenant in the Hastings and Prince Edward Regiment. He became a captain in the regiment in 1921, major in 1925 and in 1937 was promoted to lieutenant-colonel and was given command of the First Battalion. In 1942 he took over command of the 9th Anti-Tank Regiment, and remained in that post until he retired from the military in 1945. He continued as Crown Attorney of Hastings County until 1954.
Bryson Carlyle Donnan was a Freemason, an honorary director of the Belleville Club and a member of the Bay of Quinte Yacht Club. He died in Belleville General Hospital on 25 February 1963 and was survived by his wife, Connie, and three sons.