He represented Shelburne County in the Nova Scotia House of Assembly from 1906 to 1925 as a Liberal member. Irwin was the 17th Lieutenant Governor of Nova Scotia from 1937 to 1940. He was born in Shelburne, Nova Scotia, the son of Robert Gore Irwin and Isabel Archer, and was educated there.
Irwin worked for fifteen years as a travelling salesman before establishing a lumber and dry goods business at Shelburne.
Irwin was speaker for the provincial assembly from 1917 to 1925. He died in Shelburne.
They also had a brother named Archer.