Gardner signed a three-year deal with Sunderland for an undisclosed fee, believed by BBC Sport to be about £6 million, on 30 June 2011. Gardner made his debut as a substitute in the home defeat to Newcastle United on 20 August, and scored his first competitive goal on 18 September 2011 with a deflected shot that looped over goalkeeper Asmir Begović as Sunderland beat Stoke City 4–0 at home to secure their first win of the season. Gardner fell out of favour at Sunderland, and was linked with a departure in the January transfer window. However, he was re-united with former boss O'Neill when he replaced Steve Bruce as Sunderland manager in December 2011, and this prompted a change in fortune for Gardner and the Black Cats. Gardner was deployed at right back against Manchester City on New Year's Day 2012 due to an injury crisis, and helped Sunderland to a shock 1–0 win against the league leaders. Two days later Gardner, again playing at right back, scored his second goal for Sunderland, direct from a free kick 30 yards away from goal in their 4–1 away win at Wigan. Gardner was rumoured to be homesick at Sunderland in the press, and was linked with a move back to the Midlands. Sunderland rejected a loan bid for Gardner from former club Birmingham City on 19 January. Gardner scored a stunning volley from 25 yards late on in Sunderland's 2–0 win over Swansea City on 21 January.