Josh Watson swam the backstroke leg in the heat of the medley relay in Sydney 2000. In the final, Matt Welsh, Regan Harrison, Geoff Huegill and Michael Klim combined to claim the silver medal behind the United States. He finished fourth in the 100 metres backstroke behind Krayzelburg (US), Matt Welsh and Theloke (GER). At Athens 2004, he swam in the heats of the 100 metres backstroke. At the 1998 Kuala Lumpur Commonwealth Games, Watson won a silver medal in the 100 metres backstroke and a gold medal in the medley relay and in 1999 he won the 200 metres backstroke at the World Short Course Swimming Championships.