Leadbitter played for Sunderland from 2003 until 2009 after rising as a product from the team's Youth Academy before signing for Ipswich Town.

Before obtaining a regular first-team place at the club, he was loaned to Rotherham United in September 2005, where he scored once against Swansea[5] in five league games.

After his loan stay in Hibernian, he began to be selected regularly by then manager Mick McCarthy, and played in 11 of Sunderland's final 14 matches of the season.

[6] After Sunderland's relegation in 2006, Leadbitter stalled on contract talks, with many predicting he was aiming to attract the attention of a Premier League club after his impressive displays during the previous season.

However, a contract was subsequently agreed with the player claiming he only ever wanted to stay with Sunderland and, henceforth, Leadbitter played an important role in the Black Cats' revival under the management of Roy Keane.

This emotional celebration was because his father, Brian Leadbitter, had died just weeks beforehand and his ashes had been buried right on that spot under the grass on the Stadium of Light.

On 1 September 2009, Leadbitter transferred to Championship club Ipswich Town for a fee of £2.6 million, along with team-mate Carlos Edwards.

He made 50 appearances over the course of the season, scoring 6 goals, including a brace in a 3–3 home draw with Middlesbrough at Portman Road.

Leadbitter's commanding performances and selection of spectacular goals lead to him being named in the Championship PFA Team of the Year.

[22] On 14 September 2021 Leadbitter announced his retirement from football, most notably winning the EFL trophy with the club in his final season.

[23] Leadbitter came on as a late substitute replacing Gabriel Agbonlahor, in a 2–0 win in England Under 21s 2009 UEFA European Under-21 Championship qualification group, against Bulgaria.