On 18 April 2010, Petrov announced that his season was over and that he would miss the four remaining Premier League games due to a knee injury.
On 8 June 2010, it was announced that Petrov's contract had expired and that he would be leaving the club, along with Benjani Mwaruwari, Karl Moore and Sylvinho.
On 22 June 2010, it was announced that Petrov had agreed terms with Bolton Wanderers, and the free transfer was completed when the transfer window opened on 1 July. He scored his first goal for the club against Manchester United on 26 September 2010, and finished the season with three goals. His 2nd season saw him score six goals, four in the League, one in the League Cup and one in the FA Cup as Bolton were relegated from the Premier League. At the end of the season, Petrov had played enough matches (needed 30 played 35) to activate a clause in his contract, extending his contract for another season.