Trihey served as secretary-treasurer and president of the CAHL following his retirement as a player until 1904, as well as developing a successful law practice. He also served as a referee both for league and Stanley Cup play and sat on the advisory board of the Montreal Wanderers Hockey Club. During World War I, he was the lieutenant colonel commanding the Irish Rangers regiment. Trihey resigned his commission and returned to Montreal in 1917 after the British army reversed its earlier promise to send the Rangers into battle as a discrete unit, instead choosing to plug them into the front line as reinforcements, and in the wake of unrest over the Easter Rising in Ireland in 1916. Later in life, he was a partner in the law firm of Plimsoll and Coonan from the 1920s to 1932, and served as a Port Commissioner of the Montreal Harbor Commission.