In 2013, Iajour became the first African football player to be Fédération internationale de football association Club World Cup"s top scorer and Bronze Ball, advancing with Raja Casablanca into the final played against European champions Bayern Munich. Raja Casablanca Iajour began his career at his hometown club Raja Casablanca, in 2003. After staying there for four years, he moved to Football Club Chiasso.
He returned to Raja Casablanca in 2012.
In 2013, Raja qualified to Fédération internationale de football association Club World Cup as league champions of host country. On 11 December 2013, Iajour scored a goal in the 2–1 victory against Auckland City, in the play-off for quarter finals.
His team eventually defeated Monterrey with 2–1 in the quarter finals to pass in the semi-finals. On 18 December 2013, he scored a goal in the historical 3–1 victory against Atletico Mineiro in the semi-finals.
But in the final, Raja Casablanca was defeated by Union of European Football Associations Champions League holders, Bayern Munich with 2–0.
Iajour become one of the Fédération internationale de football association Club World Cup top scorers for 2013, together with Dario Conca, César Delgado and Ronaldinho. He received the Fédération internationale de football association Club World Cup bronze ball. Football Club Chiasso In August 2007 when the Arabian Clubs Tournament was finished, Mouhcine decided to stay in Switzerland without the permission of his club Raja Casablanca.
On 28 October 2007, Iajour has appeared for the first time in official match with the team of Football Club Chiasso.
In the 2005 Fédération internationale de football association World Youth Championship Iajour has scored three goals and helped to move to the semi-finals, where they were defeated 3–0 by Nigeria. ended the tournament in fourth place after a 2–1 loss to Brazil. In January 2014, coach Hassan Benabicha, invited him to be a part of the Moroccan squad for the 2014 African Nations Championship.
He helped the team to top group B after drawing with Burkina Faso and Zimbabwe and defeating Uganda. The team was eliminated from the competition at the quarter final zone after losing to Nigeria.
Club Raja Casablanca Arab Champions League: 2006 Botola: 2012-2013 Fédération internationale de football association Club World Cup runner-up: 2013 Individual International.