Originally from Esperance, Ainsworth played for local club Ports Football Club at 16 before joining WAFL club Subiaco. He won a premiership with their reserves team in 2017. He played for WA in the 2017 U18 Championships, averaging 6.5 clearances.[3] He was drafted by West Coast with pick 32,[1] and wears number 33.
In May 2018, Ainsworth signed a two-year contract with West Coast, tying him to the club until 2020.[4]
Ainsworth was delisted at the end of the Eagles' 2021 season after playing only two games for the year.[5] Shortly after his delisting, his AFL career was resurrected after being placed on the Eagles' COVID contingency list given the wave of cases in Western Australia.