He began his career at Motherwell and joined Celtic in 2004, where he won domestic honours including two Scottish Premier League titles.

[3] Though he grew up a Celtic fan, he began his footballing career at Motherwell, after they watched him score the winning goal in the final of the under-18 Scottish Schools competition.

[4] Motherwell were a financially troubled club at this time and in 2002 they were placed in administration to prevent liquidation, with 19 senior players released.

[5] Pearson's form was such that he gained a surprise call-up to Berti Vogts' full Scotland squad,[6] winning his first cap in the 1–0 Euro 2004 play-off victory over the Netherlands,[7] and attracted interest from clubs at home and abroad.

[8] However, Motherwell's financial predicament ensured they were unable to refuse any reasonable offers[9] and when Celtic manager Martin O'Neill paid £350,000 of his own personal money in January 2004, Pearson fulfilled a childhood ambition by moving to Parkhead.

He increased his international tally to six caps, but his first team opportunities were limited by injury, and he played just nine games for Celtic that season.

When Pearson recovered, he won his place back in the side and scored against Swansea City in a 1–1 away draw, but after a handful of starts suffered another injury which kept him out for 4 months.

[27] Pearson made his return from injury in the final minutes of Derby's FA Cup 5th round tie against Manchester United on 15 February 2009, but suffered setbacks on his road to recovery, finally starting again for the club against Burnley on 4 April 2009. and appearing in a further five games before the season ended, finishing the season with just 13 appearances in all competitions.

[29] Pearson returned to first team action as a second-half substitute in a 1–1 draw at Barnsley on 18 September 2010; Derby's seventh game of the 2010–11 season.

On 16 December 2014, he scored his first goal for the club in the 117th minute of second leg of the play-off semifinals against Chennaiyin FC with a neat finish with his left foot, which turned out to be the winner.

He made one appearance in Scotland's 2006 FIFA World Cup qualification campaign, as a 63rd-minute substitute for Richard Hughes in a 1–0 home defeat to Norway on 9 October 2004.

[46] Pearson earned ten caps in all for Scotland, his last being on 17 October 2007 in a 2–0 away defeat to Georgia in UEFA Euro 2008 qualifying, playing the first 66 minutes before being replaced by Kris Boyd.