Ryan Mitchell swam the breaststroke 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 eighth in the 200 metres breaststroke. In his Olympic debut at Atlanta 1996, Mitchell finished third in the B final of the 200 metres breaststroke. In 1995 and 1995, he was the silver medallist in the 200 metres breaststroke at the world short course championships.