Frederick enlisted at Inverell in January 1916 when he was just twenty years old. His father, David, signed the enlistment papers giving permission for his son to serve overseas. Frederick joined other district men to form the Second Contingent of The Kurrajongs who left Inverell together on 29 February 1916 for the Narrabri and Armidale camps.
He became a member of the 33rd Battalion, 3rd Re-enforcement which sailed from Australia on HMAT A68 Anchises in August 1916. Upon arrival in England in October, Frederick was hospitalised at Devonport with mumps. After rejoining his unit he was sent to France in November. Just before the Battle of Messines in June 1917, Frederick was wounded and returned to England where he was admitted to Guildford War Hospital with a gunshot wound to his right shoulder. Eventually the decision was made to return him to Australia by the ship Borda. He was medically discharged in May 1918 and granted a pension of thirty shillings per fortnight.
After the War he resumed his building career and married Mary Campbell at Warialda in 1927. Frederick died at Collarenabri in 1965.
Private Frederick McKenzie’s name is recorded on the Inverell Honor Roll.