On 22 June 2011, Sunderland confirmed that Larsson would join the club on a free transfer under the Bosman ruling on 1 July.
linking up with former Birmingham manager Steve Bruce.
He was given squad number 7 for the 2011–12 season.
He marked his debut with the second-half equaliser in a 1–1 draw on the opening day of the season against Liverpool at Anfield, when given room at the far post to produce a "superb first-time angled volley."
His second Sunderland goal, direct from a free kick, put his team 4–0 up against Stoke City at the Stadium of Light in their first win of the season.
Larsson scored directly from another free-kick against Arsenal at the Emirates Stadium a month later, prompting Arsenal manager Arsène Wenger to label his former player "maybe the best in the league as a free-kick-taker."

He scored the opening goal in Sunderland's 2–1 home defeat by Wigan Athletic on 26 November, which proved to be Bruce's last game in charge of the Black Cats.
Sunderland visited Wolves the following week under caretaker manager Eric Black.
With Sunderland 1–0 up, Larsson won a penalty, although replays suggested he dived.
His penalty was saved by Wayne Hennessey; less than 30 seconds later, Steven Fletcher equalised for Wolves, and went on to add a late winner.
Larsson made amends in the following game, scoring from a free kick against Blackburn Rovers in injury-time to secure a late 2–1 win in Martin O'Neill's first game as manager.
Larsson scored another free kick on 8 January in the FA Cup in a 2–0 win against Peterborough United at London Road.
In the fifth round tie with Arsenal, a quick counterattack from Sunderland saw Larsson hit the woodwork, and the ball subsequently hit Alex Oxlade-Chamberlain to put Sunderland 2–0 up and into the quarter-finals.
Larsson scored twice as Sunderland drew 3–3 with Manchester City at the Etihad Stadium on 31 March.

Larsson produced a "25-yard thunderbolt" as his first goal of the 2012–13 Premier League season against West Ham United on 12 January 2013 in a 3–0 win.
He provided the assist for Stéphane Sessègnon's goal in Sunderland's 1–0 defeat of Everton on 20 April, pushing the club clear of the relegation zone.
The strike against West Ham proved to be Larsson's only goal of the campaign, a season in which was underwhelming on both individual and club levels as Sunderland barely managed to avoid relegation.

His first goal of the 2013–14 season came on 6 November 2013, in a 2–1 win against Southampton in the League Cup.
His first league goal of the season came against Manchester United on 3 May 2014, where he scored the only goal of the game.
The result gave Sunderland their first win at Old Trafford since 1968.
After contributing to Sunderland's escape from relegation, he was given a new contract to run until 2017.

On 16 August 2014, Larsson scored a late equaliser for Sunderland in their 2–2 draw with West Bromwich Albion on the opening day of the 2014–15 Premier League season.
His second goal of the season was a free kick to open the scoring in a 1–1 draw with Everton on 9 November, and his third, another direct free kick, came in a 2–1 loss at Tottenham on 17 December.
Larsson was named Sunderland's Supporters' Player of the Year for the 2014–15 season.
On 22 June 2011, Sunderland confirmed that Larsson would join the club on a free transfer under the Bosman ruling on 1 July. linking up with former Birmingham manager Steve Bruce. He was given squad number 7 for the 2011–12 season. He marked his debut with the second-half equaliser in a 1–1 draw on the opening day of the season against Liverpool at Anfield, when given room at the far post to produce a "superb first-time angled volley." His second Sunderland goal, direct from a free kick, put his team 4–0 up against Stoke City at the Stadium of Light in their first win of the season. Larsson scored directly from another free-kick against Arsenal at the Emirates Stadium a month later, prompting Arsenal manager Arsène Wenger to label his former player "maybe the best in the league as a free-kick-taker."
He scored the opening goal in Sunderland's 2–1 home defeat by Wigan Athletic on 26 November, which proved to be Bruce's last game in charge of the Black Cats. Sunderland visited Wolves the following week under caretaker manager Eric Black. With Sunderland 1–0 up, Larsson won a penalty, although replays suggested he dived. His penalty was saved by Wayne Hennessey; less than 30 seconds later, Steven Fletcher equalised for Wolves, and went on to add a late winner. Larsson made amends in the following game, scoring from a free kick against Blackburn Rovers in injury-time to secure a late 2–1 win in Martin O'Neill's first game as manager. Larsson scored another free kick on 8 January in the FA Cup in a 2–0 win against Peterborough United at London Road. In the fifth round tie with Arsenal, a quick counterattack from Sunderland saw Larsson hit the woodwork, and the ball subsequently hit Alex Oxlade-Chamberlain to put Sunderland 2–0 up and into the quarter-finals. Larsson scored twice as Sunderland drew 3–3 with Manchester City at the Etihad Stadium on 31 March.
Larsson produced a "25-yard thunderbolt" as his first goal of the 2012–13 Premier League season against West Ham United on 12 January 2013 in a 3–0 win. He provided the assist for Stéphane Sessègnon's goal in Sunderland's 1–0 defeat of Everton on 20 April, pushing the club clear of the relegation zone. The strike against West Ham proved to be Larsson's only goal of the campaign, a season in which was underwhelming on both individual and club levels as Sunderland barely managed to avoid relegation.
His first goal of the 2013–14 season came on 6 November 2013, in a 2–1 win against Southampton in the League Cup. His first league goal of the season came against Manchester United on 3 May 2014, where he scored the only goal of the game. The result gave Sunderland their first win at Old Trafford since 1968. After contributing to Sunderland's escape from relegation, he was given a new contract to run until 2017.
On 16 August 2014, Larsson scored a late equaliser for Sunderland in their 2–2 draw with West Bromwich Albion on the opening day of the 2014–15 Premier League season. His second goal of the season was a free kick to open the scoring in a 1–1 draw with Everton on 9 November, and his third, another direct free kick, came in a 2–1 loss at Tottenham on 17 December. Larsson was named Sunderland's Supporters' Player of the Year for the 2014–15 season.
Sebastian Larsson