His eldest brother, Russell Henry Watson (1892–1941), was an Australian amateur middle distance champion, who held titles in the mile, half-mile, and 440 hurdles.

[5] Both Alf and his older brother, Edward, attended Caulfield Grammar School from 1917 to 1919.

Watson finished second behind John Sheffield in the 440 yards hurdles event at the 1936 AAA Championships.

[11][12][13] One month later he was selected to represent Australia at the 1936 Olympic Games held in Berlin, where he was eliminated in the first round of both the 110 metre hurdles contest and the 400 metre hurdles event.

[14] At the 1938 Empire Games he was a member of the Australian relay team which won the bronze medal in the 4×110 yards competition.