He spent time on loan at AFC Bournemouth in 2002, before moving to Villa's local rivals Birmingham City in 2007, where he was part of the 2011 Football League Cup Final-winning team.

[7][8] His debut for Aston Villa's first team came on 4 January 2003, in a 4–1 defeat to Blackburn Rovers in the FA Cup third round, when he came on as a substitute to replace Rob Edwards after 69 minutes.

On 15 January 2005, Ridgewell scored his first professional goal, heading in Nolberto Solano's cross in the ninth minute to open a 3–0 win over Norwich City.

[13] Ridgewell completed a move to Birmingham City for a fee of £2 million on 3 August 2007, becoming the first player to transfer between the bitter rivals since Des Bremner in 1984.

[20] He continued in that role because of the form of preferred centre-backs Roger Johnson and Scott Dann,[21] and played there as Birmingham went on a club-record 12-match unbeaten run in the top division[22] and set a Premier League record by fielding the same starting eleven for nine consecutive games.

[23] He scored a 91st-minute equaliser against Tottenham Hotspur on 30 January 2010 which ensured that Birmingham remained unbeaten at home since the previous September.

[37] He made his MLS debut on 18 July, the 62nd consecutive sellout at Providence Park, and a comeback 2–1 victory over the visiting Colorado Rapids.

[44] In December 2015, Ridgewell agreed a short-term loan with Championship team Brighton & Hove Albion, to begin when the transfer window opened on 2 January 2016 and end in time for the second half of the Timbers' preseason.

[47] The Timbers made the 2018 MLS Cup Playoffs; in the Western Conference semi-finals they defeated rivals Seattle Sounders FC on penalties.

[53] He made his debut the next day in the season opener, a 3–1 home loss to Blackpool, starting on the left of a three-man defence and being replaced by Layton Ndukwu after 52 minutes.

[58] In October 2016, Ridgewell and Portland Timbers teammate Jake Gleeson were arrested and charged with driving under the influence and refusing breathalyzer tests in Lake Oswego, Oregon.

The case against Ridgewell was dropped in January 2017 when a judge ruled that the police had insufficient cause to stop and test him, while Gleeson pleaded no contest to his charges.

[59] Ridgewell co-owns custom swimwear company Thomas Royall with fellow footballers Sam Saunders and John Terry.