Thomas Shillington Cowan was born in Aghalee, County Antrim, (Northern) Ireland on September 9, 1899. Tommy first made his name in football while starring as a centre-forward for Willowfield in the 1920-21 Intermediate League. In April 1921 Tommy moved to Belfast club Linfield.
At Linfield Tommy was moved to the outside right position. Playing in 29 games and scoring six goals, he helped Linfield win seven trophies in the 1921-22 season. Linfield winning the Irish League Championship, the Irish Cup, City Cup, Gold Cup, County Antrim Shield, Charity Cup and the Alhambra Cup.
On November 14, 1921 Tommy represented Ireland in an amateur international game against England. England won 4-1 at Leicester City’s ground in England.
At the age of 27 he emigrated to Canada. Tommy arrived in Canada on June 26, 1927 on the steamship Montcalm. On July 6 he scored one of Ulster United’s goals in a 2-0 win over Toronto Scottish in the Provincial Soccer League.
Tommy played at outside right for Ulster United against the Scottish Football Association touring team on July 11, 1927. The tourists won 3-0 in front of a crowd of 7,000 in Toronto.
On August 13, 1927 Tommy scored all four goals for Ulster United in a 4-0 win over Hamilton City in a National Soccer League game.
After the 1928 season Tommy stopped playing for Ulster United. He later moved to the United States.