Hart, along with Kerry Mayo, was released by former manager Dean Wilkins during June 2008, but after Wilkins' sacking from Brighton, were bought back to the club under manager Micky Adams, both of whom had worked with him during his first spell as manager at the club.
Hart is known for his versatility, as he has played in many numerous positions for the club such as; right-back, winger, wide midfield, centre midfield and striker during his Brighton career. He has managed to score 43 goals in over 350 games for the club.
Gary was one of the few instrumental figures that helped the club rise through the Football League and played an important part in Micky Adams back-to-back Championship winning side from 2000-2001. He has gone on to play for a further six managers with the club, Peter Taylor, Steve Coppell, Mark McGhee, Dean Wilkins, Russell Slade and Gus Poyet.
During May 2007, Hart was awarded with a new one-year contract after playing in a certain amount of games for the 06/07 season. Hart achieved a testimonial year with the Seagulls with this deal, following on from Kerry Mayo who achieved the accolade the previous season.
For the 2007/08 season Hart lost his number 9 shirt, to new signing Nicky Forster, that he had worn for the Seagulls since signing in 1998. Hart wore the number 12 for Brighton during the 2007/08 season, and changed again to number 15 for the 2008/09 season.
On the 6 December 2007, it was revealed that Hart has joined Conference South side Havant & Waterlooville on a one-month loan deal. Hart joined fellow ex-Albion player Charlie Oatway at the club who retired from the professional game in the summer of 2007 due to injury.
With an injury crisis at Brighton, Hart was recalled from his loan spell at Havant & Waterlooville on the 7 January 2008. He was involved in the squad for the first time in the 2007/08 season in the Football League Trophy game at Swansea.
On the 6 May 2008, it was confirmed that Hart, along with experienced trio Kerry Mayo, Guy Butters and Paul Reid were to be released from the club by former manager Dean Wilkins. Mayo and Hart both signed new contracts after impressing during pre-season under new manager Micky Adams.
In May 2011 the club announced that he would be released at the end of the season following the ending of his current contract, along with five other players. On the 16th of July 2011 Hart was called back to the Brighton Reserves squad for the final time by manager Gus Poyet to captain the side in their Sussex Senior Cup final against Eastbourne Borough. It was the first competitive match to be played at Brighton's new American Express Community Stadium. The home side won the game 2-0 with Hart confirming his already legendary status at the club by scoring the first goal at the new ground.
Hart signed for Eastbourne Borough on 23 July 2011.