An Australia international and New South Wales State of Origin representative three-quarter back, he played his club football for Western Suburbs, the Newcastle Knights, the St. George Illawarra Dragons and the Wigan Warriors (with whom he won the 2002 Challenge Cup).

Ainscough represented the New South Wales Rugby League team in the State of Origin series in 12 games between 1996 and 2001 (three as a replacement).

Ainscough joined St George in 1997 and played on the wing in the 1999 NRL Grand Final loss against the Melbourne Storm.

Ainscough concluded his career in the Super League with English side the Wigan Warriors in 2002 when they won the Challenge Cup.

He played in a Wigan Warriors team studded with Australians in Brett Dallas, Julian O'Neill, Adrian Lam, Craig Smith, David Furner and coached by Stuart Raper.