Swann began his domestic career for Northamptonshire. As a teenager, he was part of the U-19 World Cup winning side in 1998, a tournament that took part in South Africa (alongside future England players Owais Shah and Robert Key).

Against Leicestershire in 1998 he scored 92 and 111, his maiden first-class half-century and century. Touring South Africa and Zimbabwe with the England A-team that winter, Swann took 21 wickets at 25.61 and averaged 22 with the bat. Wisden commented,

In 1999, Swann was brought into the England squad for the final Test against New Zealand. He did not play, but featured in an ODI against South Africa following an injury to Ashley Giles. This tour also saw him miss the team bus once due to oversleeping.

In domestic cricket, Swann scored his highest first-class score of 183 in 2002, sharing a partnership of 318 with Northants captain Mike Hussey (310 not out).

Bangladesh, India, and Sri Lanka hosted the 2011 World Cup between February and April. England selected three spinners in their 15-man squad including Swann. England were knocked out in the quarter-finals. With 12 wickets from seven matches, Swann finished as England’s highest wicket-taker in the tournament. Sri Lanka toured England in May. In the first Test Swann took 7/82 to help England to an innings victory. After winning the first match, England drew the second and third to win the series. Swann was the second-most productive bowler in the series, taking 12 wickets in the series at an average of 23.58, and was ranked as the second best Test bowler in the world. England won the following five-match ODI series 3–2. Swann took eight wickets and in the process rose to the No. 1 spot in the ICC’s ODI bowler rankings. It was the first time since Steve Harmison in 2004 that an England bowler had held the No. 1 position in either Test or ODI cricket.

He moved to Nottinghamshire in 2005, and finished the season of 2007 with 516 runs and 45 wickets, leading to his recall to the England side against Sri Lanka. While England fell heavily in defeat during the first match, Swann hit 34 to help seal victory in the second, and took four for 34 and hit 25 in the third as England took a two-one lead in the series.

Following a loss of form by Monty Panesar, alongside whom Swann had played for Northamptonshire, Swann made his Test debut against India in December 2008, and made an immediate impact, dismissing Gautam Gambhir with his third delivery and Rahul Dravid with his sixth, both lbw, thus becoming only the second player in Test history after Richard Johnson (also for England) to take two wickets in his first Test over.

In the Third Test in the West Indies in February 2009, he was brought back into the Test fold following the poor form of Panesar, and in this match collected his first five-wicket haul in a Test, 5 for 57 in the West Indies’ first innings, including two wickets in two balls. This was the second-best performance ever by any spinner in Antigua. Swann also collected five wickets in the first of the West Indian innings in the Fourth Test.

England’s next assignment was a tour of Bangladesh in March 2010. The ODI series was a 3–0 whitewash for England, with Swann taking seven wickets, behind just seamer Tim Bresnan with eight. Even with a weakened side, taking the opportunity to blood new players, England were expected to easily win the two-match Test series. In the first match Swann took his maiden ten-wicket haul in Tests; it was the first time an off-spinner had taken ten wickets in a match for England since Jim Laker took 19 against Australia at Old Trafford in 1956. The pitch at Chittagong offered little for fast bowlers, leaving Swann with the bulk of the work. The performance, claiming 10/217 from 78.3 overs, earned him the Man of the Match award and raised him to second place in the ICC’s Test bowling rankings. Claiming six wickets in the second Test to guide England to a 2–0 whitewash, Swann was named Man of the Series.

Swann is noted for being an attacking spinner, generally delivering the ball with plenty of flight and bounce. He is also capable of subtle changes of pace. Unlike many contemporary off-spinners he does not bowl the doosra. Instead, his variations include a well-developed arm ball, and also a flatspinner/slider delivery that he has nicknamed his “flying saucer ball” that rotates around its vertical axis and generally bounces straight on. Swann also noted that he has a very different grip to the textbook grip of simply resting the tip of the index and middle fingers on the seam. He jams the seam as far as their second knuckles and almost coming out like a googly on the back of the hand on release. Because of this, he can spread the two fingers very wide apart. Commentator Peter Roebuck suggested in March 2010 that Swann’s success has been due as much to his attitude as skill:

Swann married his wife Sarah on 29 January 2010. They live in Nottingham with their three children, Wilfred (born 17 February 2011), Charlotte (born 18 October 2012) and Jessica (born 2016). He also has an interest in football and revealed on the BBC’s Football Focus that he supports Newcastle United and Blyth Spartans.

On 2 April 2010 he was stopped by police in West Bridgford, Nottingham following a party and was arrested after providing a positive breath test. He was charged in June, to appear in court in August, and initially told court that he was on his way to purchase screwdrivers in order to rescue his cat from under the floorboards. Due to his cricketing commitments, the trial had several adjournments before he was cleared in February 2011, on the grounds that the blood sample could not be used as evidence.

A recurrence of an old elbow injury prevented Swann from joining England on the tour of New Zealand in March 2013. Panesar took his place as lead spinner in the side, but managed just 5 wickets costing 70 runs each as England drew the three-Test series 0–0. After undergoing surgery on his elbow, Swann was fit enough to return to the side when New Zealand toured England in May and June 2013.

On 21 December 2013, Swann announced his retirement from all cricket with immediate effect. At this point, England were 3–0 down in the Ashes 2013-14 series.

Swann became a summariser for the BBC’s Test Match Special in February 2014.