Simon Gillies joined Canterbury in 1988 as a lock forward and started his initial season in reserve grade and received the opportunity to play first grade against Cronulla in the Semi-Final as a replacement.

In 1991, Simon started the season in first grade and became a regular member of the team.

In 1992, Simon played every first grade game before missing most of 1993 with a broken leg, however Simon did return late in the season to play in the Preliminary Final against Brisbane as a replacement.

Simon returned in 1994 to be a regular replacement and played the Grand Final against Canberra as a replacement.

In 1995, Simon became a regular member of the first grade team playing in every game that season, including the Premiership wining team against Manly.

In 1996, Simon was appointed captain. He captained Canterbury on 41 occasions from 1995 to 1998.

Unfortunately, Simon missed half of the season with a knee injury, ending his run of consecutive games to 63.

In 1997, Simon played three games for NSW in the Tri-Series and played in the Preliminary Semi-Final against Penrith.

At the close of his career with the Bulldogs, Simon had  a one year stint in England with the Warrington Wolves.  Upon his return to Sydney he took up a coaching role at Cabramatta then spent 3 years at the Sharks in various coaching and training roles.

In 2004, Simon was nominated for the Berries to Bulldogs 70 Year Team of Champions.

Simon joined the rental industry in 2005 and is currently employed as the Sales and Marketing Manager for Coates Hire NSW.