On 16 July 2007, Richardson joined Sunderland for an undisclosed fee, reported to be in the region of £5.5 million.
He signed a four-year contract with Sunderland, under the management of his former United captain Roy Keane.
After an indifferent start, it was discovered that he had a stress fracture of the spine.
This led to him being out of action for almost four months.
He scored his first goal for Sunderland on 29 December 2007 against Bolton Wanderers.
Richardson scored two goals in the 2–0 win against Portsmouth at the Stadium of Light on 13 January 2008, also striking the bar to miss out on his hat-trick.
Since then he suffered a hamstring injury in training then this injury recurred in Sunderland's 3–0 defeat to Liverpool at Anfield.

On 23 August 2008, Richardson scored against Tottenham Hotspur in the 56th minute, in a 2–1 win at White Hart Lane.
Richardson took a free kick that hit the post three times at Fulham on 18 October, and later had another free kick disallowed as Pascal Chimbonda was adjudged to be pushing in the wall.
On 25 October 2008, Richardson scored the winning goal in the Tyne–Wear derby, with a free kick.
Richardson attracted interest from Bolton Wanderers in the 2009 January transfer window, but manager Ricky Sbragia insisted that he was not for sale.

Richardson scored his first goal of 2009–10 with an equaliser against West Ham United, which ended 2–2.
Richardson was used in several positions throughout the season, whilst predominantly featuring in central midfield he also played at left back – his performances there led to many touting him as a surprise World Cup inclusion.

In the buildup to 2010–11, Richardson committed his future to the club by signing a new three-year contract.
Soon after, he became first-choice left back at the club citing Brazilian full-back Maicon as inspiration for taking up his new position, saying "I watched the World Cup and saw the way guys like Maicon were bombing forward – and I thought "I can do that".
He opened his scoring account for the season on 22 January away to Blackpool scoring two goals in the first half.
After deploying him in an attacking role, Sunderland manager Steve Bruce hailed Richardson's versatility saying "I must have asked him to play in five or six positions this season and certainly in that position he enjoys it, it's something he revels in".
He then added "He was the outstanding player on the pitch.
In the first half he was brilliant, his pace was superb."
Richardson scored directly from a free kick in Sunderland's next match, a 4–2 home defeat to Chelsea.
Richardson made his 100th Premier League appearance for Sunderland at home to Tottenham Hotspur on 12 February, assisting Asamoah Gyan's opener in a 2–1 defeat.

Richardson's first goal of 2011–12 came in a 2–1 defeat at Norwich.
Richardson was on target again in a defeat at Wolves under caretaker manager Eric Black, following Steve Bruce's departure.
In this match against Wolves on 4 December 2011, Richardson scored the opening goal, a long range shot from the left, and celebrated by removing his shirt, revealing a T-shirt with the slogan "I belong to Jesus".
He was booked for removing his shirt.
Sunderland went on to lose the match 2–1.Under new manager Martin O'Neill, Richardson began to make impressive progress after being shifted into his preferred left wing position, making another contribution in his team's 3–2 victory away to Queens Park Rangers on 21 December 2011 after setting up two goals from corner kicks.
On 18 February 2012, he scored his first FA Cup goal for the club against Arsenal at the Stadium of Light in the fifth round in which he scored the first goal in Sunderland's 2–0 win.
On 16 July 2007, Richardson joined Sunderland for an undisclosed fee, reported to be in the region of £5.5 million. He signed a four-year contract with Sunderland, under the management of his former United captain Roy Keane. After an indifferent start, it was discovered that he had a stress fracture of the spine. This led to him being out of action for almost four months. He scored his first goal for Sunderland on 29 December 2007 against Bolton Wanderers. Richardson scored two goals in the 2–0 win against Portsmouth at the Stadium of Light on 13 January 2008, also striking the bar to miss out on his hat-trick. Since then he suffered a hamstring injury in training then this injury recurred in Sunderland's 3–0 defeat to Liverpool at Anfield.
On 23 August 2008, Richardson scored against Tottenham Hotspur in the 56th minute, in a 2–1 win at White Hart Lane. Richardson took a free kick that hit the post three times at Fulham on 18 October, and later had another free kick disallowed as Pascal Chimbonda was adjudged to be pushing in the wall. On 25 October 2008, Richardson scored the winning goal in the Tyne–Wear derby, with a free kick. Richardson attracted interest from Bolton Wanderers in the 2009 January transfer window, but manager Ricky Sbragia insisted that he was not for sale.
Richardson scored his first goal of 2009–10 with an equaliser against West Ham United, which ended 2–2. Richardson was used in several positions throughout the season, whilst predominantly featuring in central midfield he also played at left back – his performances there led to many touting him as a surprise World Cup inclusion.
In the buildup to 2010–11, Richardson committed his future to the club by signing a new three-year contract. Soon after, he became first-choice left back at the club citing Brazilian full-back Maicon as inspiration for taking up his new position, saying "I watched the World Cup and saw the way guys like Maicon were bombing forward – and I thought "I can do that". He opened his scoring account for the season on 22 January away to Blackpool scoring two goals in the first half. After deploying him in an attacking role, Sunderland manager Steve Bruce hailed Richardson's versatility saying "I must have asked him to play in five or six positions this season and certainly in that position he enjoys it, it's something he revels in". He then added "He was the outstanding player on the pitch. In the first half he was brilliant, his pace was superb." Richardson scored directly from a free kick in Sunderland's next match, a 4–2 home defeat to Chelsea. Richardson made his 100th Premier League appearance for Sunderland at home to Tottenham Hotspur on 12 February, assisting Asamoah Gyan's opener in a 2–1 defeat.
Richardson's first goal of 2011–12 came in a 2–1 defeat at Norwich. Richardson was on target again in a defeat at Wolves under caretaker manager Eric Black, following Steve Bruce's departure. In this match against Wolves on 4 December 2011, Richardson scored the opening goal, a long range shot from the left, and celebrated by removing his shirt, revealing a T-shirt with the slogan "I belong to Jesus". He was booked for removing his shirt. Sunderland went on to lose the match 2–1.Under new manager Martin O'Neill, Richardson began to make impressive progress after being shifted into his preferred left wing position, making another contribution in his team's 3–2 victory away to Queens Park Rangers on 21 December 2011 after setting up two goals from corner kicks. On 18 February 2012, he scored his first FA Cup goal for the club against Arsenal at the Stadium of Light in the fifth round in which he scored the first goal in Sunderland's 2–0 win.
Kieran Richardson