Born in Brussels, Belgium, Haroun began playing football at his local club Scup Jette.

[6][7] At the start of the 2004–05 season, Haroun made his UEFA Intertoto Cup debut, coming on as a 67th-minute substitute, in a 2–0 win against Borussia Dortmund to progress to the next round through away goal.

At the start of the 2005–06 season, Haroun made his UEFA Cup debut, coming on as a 69th-minute substitute, in a 3–0 win against Liepājas Metalurgs to progress through to the next round.

[15] He made another UEFA Cup appearance in a 2–2 draw against Litex Lovech, but Genk were eliminated in a return leg after losing 1–0.

Ahead of the 2006–07 season, Haroun was linked a move away from Genk, as they were trying to sell him in the summer transfer window but stayed at the club.

[31] However, he was demoted to the substitute bench for the next two matches for the side, due to strong competition in the midfield and attacking positions.

[32] Haroun made his return to the starting line–up against Germinal Beerschot on 25 August 2007, and set up the club's second goal of the game, in a 2–1.

[36] Amid the transfer speculation, Haroun scored his first goal of the season, in a 5–1 loss against Cercle Brugge on 20 January 2008.

[42] After spending weeks due to his international commitment with Belgium U23, Haroun made his Germinal Beerschot debut, where he started the whole game, in a 1–0 loss against K.V.C.

[60] Despite previously stating Haroun would not become a top–scorer earlier in the 2009–10 season, he finished as the club's top scorer with eleven goals in thirty–two appearances in all competitions.

Faris has looked good in training", "He's fit and athletic, has a love of the game and is full of enthusiasm.

"[72] Haroun made a dream start to his Middlesbrough career, scoring on his debut in a 3–1 win over Birmingham City on 21 August 2011.

[73] His first team start came three days later on 24 August 2011 when he helped Middlesbrough to a 2–0 victory over Peterborough United in the League Cup second round.

[82] It wasn't until on 8 December 2012 when Haroun returned to the starting line–up against Peterborough United and scored his second and third goals of the season in a 3–2 win.

[92] Haroun made his Blackpool debut, starting the whole game, in a 2–0 loss against Blackburn Rovers on 1 February 2014.

[93] Since making his debut for the club, he started the next four matches before being demoted to the substitute bench for the rest of the season.

[94] At the end of the 2013–14 season, making nine appearances in all competitions, Haroun was released by the club after they decided not to offer a new contract.

[96] Haroun made his Cercle Brugge debut, playing in the midfield position, in a 4–0 loss against Gent on 22 November 2014.

[98] However, Haroun suffered ankle injury during a 2–0 win against RSC Charleroi on 17 January 2015 and missed two matches as a result.

[100] As a result, Haroun was sidelined for a month and didn't make his return on 15 March 2015, in a 3–2 loss against KV Mechelen.

[101] He played four more matches, as Cercle Brugge lost Play-Off III to SK Lierse and relegate to second division.

[119] After serving a one match suspension, he scored on his return, in a 3–2 loss against Royale Union Saint-Gilloise on 9 October 2016.

"[123] Haroun made his Royal Antwerp debut against KSV Roeselare, starting the whole game, in a 1–0 win on 6 January 2017.

[124] Since making his debut for the club, he quickly established himself in the starting eleven, playing in the midfield position.

[125] However, during a match against KSV Roeselare on 18 February 2017, Haroun suffered a hamstring injury and had to be substituted in the 36th minute, as they won 2–1.

[126] After being sidelined for one match, he made his return to the starting line–up against KSV Roeselare in the first leg play–offs final and set up the club's first goal of the game, in a 3–1 win.

[127] In the second leg play–offs final, Haroun started the match and helped the side win 2–1 to gain promotion to the Belgian First Division A next season.

In the 2018–19 season, Haroun continued to establish himself in the starting eleven, playing in the midfield position, as well as, captain.

[176] Haroun later made three more appearances by the end of the year, as the national side unsuccessfully for the UEFA Euro 2008 tournament.

[180] Faris is the elder brother of Nadjim Haroun and the cousin of Kévin Nicaise, both of whom are members of the Chad national football team.