Impressive displays for Najaf FC in the 2007 AFC Champions League, where he scored two goals in six matches, earned Karrar Jassim Mohammed a move to Qatar where he signed for Al Wakra at the start of June 2007. In 2009 Karrar signed for Iranian side Tractor Sazi F.C. for one season. During a Tractor Sazi match, Karrar was banned for 9 games following an incident in which he slapped the match assistant referee. The ban was later reduced to 5 and eventually to 3 games. He was released in May 2011 by Tractor Sazi for his disrespectful behavior toward referees. On 4 June 2011, Karrar joined the Tehran based football team Esteghlal on a two-years contract. The 24-year-old striker has joined Esteghlal but he was fired in January 2012 during mid-seasion after a dispute with midfielder, and team vice-captain Mojtaba Jabbari. He then loaned to Shahin Bushehr and then moved to Ajman and a loan to Najaf FC.
On 4 July 2014, Karrar returned to Esteghlal with signing a two-year contract.