As a junior player, Youl formed a highly successful doubles partnership with his fellow Australian player Mark Kratzmann. In 1983, the pair won the Boys' Doubles titles at the French Open, Wimbledon and the US Open. In singles, he reached three slam finals, attaining a ranking as high as No. 5 in the junior world rankings in 1983.
He retired from the professional tour in 1994 (playing one Challenger event the following year). Since retiring as a player, he has worked as a tennis coach and is the current State and National High Performance Academy Coach in Hobart, Tasmania.