Thornton played for Rangers from 1936 to 1954, then became a manager with first Dundee and then Partick Thistle. He later returned to Rangers as assistant to Davie White in the summer of 1968 and was briefly caretaker manager in 1969 after White's dismissal. Thornton then worked as assistant to William Waddell until 1972. The side won the two matches that he took charge. Thornton is one of Scotland's all-time top scorers, with 139 League goals.