On 26 July 2010, Scottish Premier League club Celtic signed Hooper for £2.4 million. The move provided him with great experience, despite his young age of 22 when joining and kept him grounded. On 4 August 2010, Hooper scored on his debut for the club, against Portuguese Primeira Liga club Braga in the Champions League third qualifying round. Hooper tore his calf muscle in a friendly against Blackburn Rovers just four days later on 8 August, keeping him out of action for almost six weeks.