 Gibson was elected to represent the safe Labor western Sydney electorate of Londonderry in 1988, and re-elected as the 1991 and 1995 state elections.For the 1999 election, Gibson transferred to Blacktown, and was re-elected at the 2003 and 2007 state elections.During his term in Parliament, he was chair of the Joint Standing Committee on Road Safety (Staysafe), a member of the Standing Committee on Public Works, chair of the Standing Committee on Broadband in Rural and Regional Communities, and a member of the Public Accounts Committee.