His career was troubled by injury; he once notably played for 45 minutes against Arsenal at the Emirates Stadium with a broken leg.

Reid gained a reputation for his strong, driving runs and phenomenal long range shooting ability, memorably scoring from 35 yards against Norwich City on the opening day of the 2001–02 season to set Millwall on their way to a 4–0 victory.

On 2 May 2006, Reid scored the goal that secured Blackburn's place in the 2006–07 UEFA Cup, a header that gave them a 1–0 win over Chelsea.

[10] On 19 November 2009, Reid signed on loan for Queens Park Rangers (QPR) in an attempt to recapture his career from injury.

He, along with other players, appeared in a Libertines video (fronted by QPR fan Pete Doherty) celebrating the bands re-union.

[12] He made his debut against his previous loan club, Queens Park Rangers, on 6 March 2010, playing at right back in the 3–1 defeat at Loftus Road.

[14] On 26 May 2010, Reid joined West Brom following their promotion to the Premier League on a permanent basis after signing a two-year contract.

[17] After being released by West Bromwich Albion at the end of the 2013–14 season Reid was initially considering taking up a coaching role at the Hawthorns.

However, after being approached by newly promoted Burnley, managed by his former Millwall teammate Sean Dyche he opted to stay on playing and signed a one-year contract at Turf Moor.

Reid was made the captain of the Republic of Ireland football team for their 16 August 2006 friendly match against the Netherlands.

[28] He worked for West Brom until the end of the 2018–19 season, before joining Steve Clarke's backroom staff at the Scotland national team in May 2019.

[3] In October 2022, Reid revealed that he had left his job as Nottingham Forest assistant manager in order to begin studying to qualify as a counsellor.