Chadwick began his career at Manchester United where he made 25 Premier League appearances in four seasons. While at Old Trafford he spent time out on loan at Reading and Burnley before joining West Ham United on a permanent basis in the summer of 2004. He spent a season with the Hammers before joining Stoke City on loan in August 2005 before making the move permanent in January 2006. He remained at Stoke until November 2006 making 55 appearances before joining Norwich City. Injuries restricted his time at Carrow Road and he moved to Milton Keynes Dons in October 2008. In March 2014, Chadwick joined Cambridge United, the club he supported as a child. He was released at the end of the 2014–15 season.
Born in Cambridge, Chadwick came up through the Manchester United youth system; the majority of his appearances for Manchester United at senior level were in League Cup matches or against lower profile teams in the Premier League. He scored two league goals for Manchester United, one against Bradford in January 2001 and the other against Leeds in March 2001.
Chadwick joined West Ham United on a free transfer at the beginning of the 2004–05 season. In his season at West Ham he scored once in the league, against Leeds.
Chadwick joined Stoke City on loan at the start of the 2005–06 season. He made his Stoke City debut against Sheffield Wednesday on 6 August 2005. Chadwick's impressive performances lead to a permanent deal in January 2006 with Stoke paying £100,000 for his services. Chadwick's subsequent performances earned him many fans at Stoke City. Chadwick's goal in the F.A Cup Fourth Round against Walsall was voted goal of the round in 2006. The following season did not start off very well for Chadwick as in the opening match of the season against Southend United, Chadwick fainted and was taken to hospital. It was later revealed that he was only dehydrated.
On 27 June 2006, Norwich City manager Nigel Worthington confirmed that he was interested in signing Chadwick from Stoke, but Stoke City rejected Norwich's approach for the player.
On 13 November 2006, Worthington's replacement, Peter Grant, signed Chadwick, initially on loan, with a view to a permanent deal in January 2007. The proposed fee was £220,000, with an additional £100,000 if Chadwick helps the Canaries gain promotion. Chadwick immediately made an impact at Carrow Road by scoring on his debut against arch rivals Ipswich Town. He was injured in the latter stages of that game, and the injury kept him out for most of the remainder of the season. On 3 January 2007 Chadwick signed a 2 and a half-year deal for Norwich City.
Chadwick made his long-awaited comeback from injury as a substitute in the 1–0 win over Birmingham on 13 March 2007, and also featured in another 1–0 victory over Stoke on 17 March 2007 as he attempted to regain match fitness. His injury problems, however, continued into the following season as he struggled for fitness.
On 4 October 2008, Chadwick made his Milton Keynes Dons debut in their 4–0 defeat of Millwall after joining the League One club on an initial three-month loan from Norwich City on 1 October 2008. On 18 October 2008, Chadwick scored his first goal for the club, equalising late on to secure a 2–2 draw against Crewe Alexandra. He then scored a brace for the Dons in the 2–1 away victory over Leyton Orient. Shortly after, he picked up an injury and returned from his loan early. On Wednesday 31 December 2008, Chadwick joined the Dons on a two and a half-year deal, starting 1 January 2009. At the end of the 2009–10 season Chadwick was voted the Milton Keynes Dons Player of the Season. He won the award for the second year running at the end of the 2010–11 season. On 2 March 2013, Chadwick signed a 2-year extension to his MK Dons deal.
On 18 March 2014 Chadwick joined his home town club Cambridge United on loan. He made his debut the same day in a 2–1 home win against Welling United. Chadwick signed permanently for Cambridge on 7 June 2014. At the end of the 2014–15 season the club did not offer him a new deal when his contract expired.
After leaving Cambridge United, Chadwick signed for Isthmian League Division One North side Soham Town Rangers in November 2015. He spent one season at Soham before returning to Cambridge as a full-time coach in the club's academy.As of 4 May 2015
Manchester UnitedPremier League: 2000–01
Cambridge UnitedConference Premier play-offs: 2013–14