Glasgow born right half Duncan McKenzie began his career at Scottish Division Two side Albion Rovers. He was an ever-present for Rovers during the 1931-32 season and departed the club at the end of the campaign to join Third Division (South) Brentford, making his Football League debut at Coventry in August 1932. However he only made two appearances as The Bees were promoted to the Second Division as Champions. He broke into the Brentford first eleven in January 1934 and played 31 games during the next campaign as Brentford won the Second Division Championship in 1934-35.
He made regular appearances in Brentford’s first (and so far only) spell in the top flight, and was an ever present during their 1936-37 campaign. McKenzie’s form in Division One for Brentford led to a call up to the Scotland team for a British Home Championship match versus Ireland on 10th November 1937. Included in the lineup with Brentford teammate and fellow debutant Bobby Reid, McKenzie helped the Scots to a 1-1 draw at Pittodrie. However new signing Buster Brown caused McKenzie to ask Brentford for a transfer in 1938. McKenzie made 162 appearances and scored 10 goals during his six years with The Bees.
McKenzie transferred to Division One side Middlesbrough in May 1938 for a £6,000 fee. He made 31 appearances, scoring once for Boro, before his professional career was halted by the breakout of the Second World War in September the following year.
McKenzie returned to Brentford as a guest during the Second World War, making over 150 appearances. The highlight of his time back at Griffin Park was winning the 1942 London War Cup at Wembley Stadium. However before the end of the War he retired from professional football, emigrating to the United States.