Hooper started his career at non-League club Grays Athletic in 2003. While there he won the 2004–05 Conference South, as well as the FA Trophy twice in 2005 and 2006.
After this Championship club Southend United signed him on a free transfer in 2006. He was loaned out twice by the club, on a three-month loan to League One club Leyton Orient in 2007 and a six-month loan to League Two club Hereford United in 2008. Scunthorpe United signed him in 2008, for a fee of £175,000. After two years he was signed by Scottish Premier League club Celtic for £2.4 million. In his first season with the club he was the top scorer (22 goals in all) and also won the 2011 Scottish Cup.
Hooper has scored in the Premier League, Championship, League One, League Two, FA Cup, League Cup, Football League Trophy, FA Trophy, UEFA Champions League, UEFA Europa League, Scottish Cup, Scottish League Cup and the Scottish Premier League, the first and only player to achieve this feat.[3] On top of this, he has also scored in the Conference National, Conference South, A-League and the Indian Super League.[4][5]
Hooper was born in England but has not represented the national team at any level. In March 2011 it was thought that he may be eligible to represent Scotland. However, this possibility was later closed off. Since his move to Celtic he has been considered for England duty and was called up to the under-21 squad for a friendly but had to pull out due to injury. He was then included in the provisional squad for the 2011 UEFA European Under-21 Championship but did not go to the tournament.
