[4] As a youngster, Collins played in the youth teams of local sides Shaftesbury and Pill before joining Cardiff City at the age of 15.

[10] Lawrence and his coaching staff would settle on playing Collins as a defender and he went on to make 86 appearances in all competitions for Cardiff, scoring six goals.

[18] Due to injuries to new signing Matthew Upson and 2005–06 Hammer of the Year Danny Gabbidon, Collins was given the chance to form a centre-back partnership with Anton Ferdinand towards the end of the 2006–07 season.

[citation needed] On 28 January 2008, it was announced that Collins would be out for a year after suffering severe ligament damage in a West Ham reserve game against Portsmouth.

[19] His injury kept him out for nine months and on 26 October 2008, Collins returned to first team action, starting in West Ham's 2–0 loss to Arsenal at Upton Park.

Collins played the full ninety minutes of the League Cup Final at Wembley on 28 February 2010, which saw Aston Villa beaten 1–2 by Manchester United.

In March 2011, manager Gérard Houllier fined Collins and fellow centre-back Richard Dunne two weeks' wages after what was reported as "a boozy row with club staff during a team-bonding exercise".

[27] On 18 August 2012, Collins started alongside Winston Reid in a 1–0 home win against his former club, Aston Villa on the opening day of the 2012–13 Premier League season.

[34] Collins' final appearance of his 214 games in all competitions for West Ham came in a 3–1 win against Everton on 13 May 2018, being handed the captain's armband by Mark Noble following his introduction as a late substitution.

[35] Collins had been training at Aston Villa following his release from West Ham United and impressed manager Dean Smith, being offered a five-week contract in December.

However, he injured his calf in his first training session after signing the short-term deal, potentially ruling him out for its duration, leading Collins to cancel the contract.

[45] On 7 September 2012, in a 2014 World Cup qualifying game against Belgium, he was given a straight red card for a two-footed lunge on Guillaume Gillet, Wales went on to lose the match 2–0.