Abdellaoue got his debut for Skeid in 2007, and played a total of six games during the relegation campaign from the First Division, the second tier in Norwegian football. He was loaned out to Lillestrøm and played games for their reserve team in Norwegian Second Division, scoring one goal, before returning to Skeid. In September 2008, Abdellaoue and his teammate Dawda Leigh signed for Norwegian Premier League side Vålerenga under the Bosman rule, and joined the club on 1 January 2009.
On 13 April 2009, Abdellaoue scored his first league goal for Vålerenga in a 2–0 victory away to Lillestrøm.
In the 2010 season, he was named top-scorer of the Norwegian Second Division avd. 1 with Vålerenga"s B team, scoring 27 goals.
He scored 13 in that division the season before with the same team Abdellaoue spent the 2011 season loaned out to Tromsø Illinois, where he became the top scorer of Tippeligaen with 17 goals.
He finished runner-up in the league with Tromsø.
After he returned from Tromsø, Vålerenga rejeceted a 5 mill NOK offer for him from F.C. Copenhagen in January 2012. Mostafa joined Football Club Copenhagen in January 2012. Mostafa scored his first goal in a friendly against Football Club Anzhi.
In his 3rd match he scored twice against his former club Vålerenga IF in his debut at Parken.
On 31 August 2013 Abdellaoue was sent on a 1-year loan deal to OB. In July 2014, Abdellaoue returned to the Tippeligaen permanently by signing for Aalesunds FK.
"Mos" made his debut for the senior team when he replaced Thomas Sørum at half time in a 1–1 friendly draw against Denmark on 15 January 2012.