Dundee born outside left Dan Thomson began his football career with California United from where he joined Scottish League club Falkirk in 1920 before signing for Aberdeen in May 1923, against whom he’d impressed scoring twice in a match for Falkirk. He scored once in 11 appearances for The Dons before joining Forfar Athletic in August 1924. But a month later he moved to St Johnstone, having a spell on loan at St Mirren in March 1925 where he scored once in 2 appearances for The Buddies, before being signed by Third Division (South) club Bristol City for £250 in February 1926.
He made his Football League debut against Exeter City towards the end of the month and made 6 appearances for The Robins before the season end, but transferred to Bournemouth & Boscombe Athletic in the summer of 1926, where he scored twice in 27 appearances for The Cherries as they finished seventh in the Third Division (South). He moved on again the next summer, joining Torquay United where he scored twice in 11 appearances before losing his place in the new year of 1928. He joined Walsall that summer, but appeared only twice for The Saddlers that August before leaving the professional game.
His twin brother Douglas Thomson played for Dundee Hibernian, Aberdeen and Grimsby Town.