Career
After a successful career at Cherry Orchard in 1997 Dempsey signed a 4-year contract with and moved to Merseyside soon after his 16th birthday. Dempsey returned to Bray where over two spells he scored a total of over 5 goals in 58 total appearances. In 2002 he was signed by Scottish side Dunfermline Athletic where he made 80 league appearances over a three-year period, scoring seven league goals.
He scored on his debut against Celtic at Parkhead in front of 66,000 fans.
In his second season he helped Dunfermline into the 2004 Scottish Cup Final against Celtic in what was the great Henrik Larsson"s last game. When Jimmy Calderwood left Dunfermline to manage Aberdeen he wasted no time in signing Gary on a two and a half-year deal.
The central midfielder made an uneasy start to his Aberdeen career. Although blessed with fine technical ability and good vision, Dempsey struggled with the physical rigours of the SPL in the Aberdeen midfield.
Under pressure from a large section of the Dons support, Dempsey travelled to Doncaster to spend a time on trial with Doncaster Rovers in January 2006.
A move failed to materialise, and although Dempsey returned to Aberdeen, his future at the club looked bleak. But as the 2005-2006 season drew to a close, he forced his way back into the first team picture after a number of fine bit-part performances. On 26 March 2007, Aberdeen announced that he had rejected their final contract offer, and shortly afterwards he signed for Yeovil Town.
Street Patrick"s Athletic announced his signing on 31 January 2008.
In November 2008 he was suspended after admitting betting against his own team albeit in a game in which he was not appearing. He signed for Darlington along with former Shamrock Rovers striker Tadhg Purcell in January 2010.
He was released by the club following their relegation from League 2, along with 13 other players. On 30 July 2010, Dempsey signed for former club Bray Wanderers He then went on to decline a new contract at Bray to sign for Waterford United.
In only his third game he went on to score his first for the club where he hit a free kick from 25 yards, in what was the only goal vs Salthill Devon.
He re-signed for Bray Wanderers on 11 January 2013. In July 2014 Dempsey signed for Shelbourne F.C. in the league of Ireland First Division. He said after agreeing to play as an amateur for Aberdeen: I would rather be on the dole than play for Dunfermline.
Club Individual.