Born in Hurlford to James and Jessie Turnbull of 1 Gibson Street, Kilmarnock, Ayrshire, Turnbull started his football career with his hometown club, Hurlford Thistle. He later moved to Manchester City. In 1905, City was found guilty of malpractice relating to payments of its players, and the entire squad was suspended from playing football. When the ban was lifted on 31 December 1906, Turnbull moved to City's crosstown rivals Manchester United, along with Billy Meredith, Herbert Burgess and Jimmy Bannister. His first game for United came on the next day, 1 January 1907, against Aston Villa. Along with Meredith, he helped the club to their first championship in 1908 and the 1909 FA Cup, scoring the only goal in the final, against Bristol City. In 1908 alone, he would score 27 goals in 25 games. In February 19, 1919, Turnbull scored the first ever goal at Old Trafford, in a 4-3 loss against Liverpool. He would go on to score 100 goals for the club in 245 games. His final game for the Reds came against Sheffield United in 1915.
Turnbull died at Arras, France, aged 32, on 3 May 1917 while serving as a Lance Sergeant in the Eighth Battalion of the East Surrey Regiment of the British Army during the First World War. His body was never found and he is commemorated on the Arras memorial 
Turnbull, who was married and had four children, had received a lifelong ban from football in 1915 along with several others players after being found guilty of match-fixing. He was posthumously re-instated in 1919.
- Manchester City
- Manchester United