A Tonga and Australia international, and New South Wales State of Origin representative five-eighth or lock, he played club football for Sydney's Western Suburbs Magpies, Canterbury-Bankstown Bulldogs and the Parramatta Eels, finishing his career in the Super League for the London Broncos.

[5] He began playing rugby league as an Eastern Suburbs junior with Woolloomooloo Warriors and then Paddington Colts.

He played for Zetland Magpies alongside players such as Jim Serdaris and Terry Hill who went on to make First Grade also.

Dymock began his first-grade club career in the 1991 NSWRL season at the Western Suburbs Magpies, opposing Wally Lewis and scoring two tries in his debut.

During the 1995 season, Dymock, along with Dean Pay, Jason Smith and Jarrod McCracken reneged on their Australian Super League contracts, giving 'unfair inducement' as their reason which was later supported in the courts.

On 14 July 2011, Jim Dymock was announced as the Canterbury club's new head coach, after Kevin Moore stood down from the position.