In August 2007, he was Singapore's winner of Nike's 'Who's The Next' contest and secured a training stint at FC Barcelona's famed academy, La Masia.

He trained at the Catalans' youth academy for a week, along with 13 other players from six Asia Pacific countries including South Korea and Japan.

[3] 2008 proved to be a difficult year for Hariss as he tore his ligaments in a league match against Super Reds on 26 May when Oh Ddog Yi fell on his right knee.

The injury ruled him out for a year, causing him to miss the rest of Singapore's World Cup qualifying campaign as well as the 2008 ASEAN Football Championship.

[4][5] With the help of the Football Association of Singapore and the national team coach Raddy Avramovic, Hariss underwent a 10-day trial with Chinese Super League side Shanghai Shenhua in July 2010, but was ultimately not offered a contract.

[7] The duration of six weeks that Hariss required for the recovery of his fracture eventually meant that he missed out on a second consecutive ASEAN Football Championship.

Hariss' goalscoring form against Sabah would continue when the stand-in captain scored his first career hat-trick in a record 9–0 win on 16 June.

Hariss made 34 appearances and scored 5 goals in all competitions as LionsXII finished runners-up in their first season back in Malaysian football.

Hariss played a pivotal role for the club as LionsXII capped the successful 2013 season as eventual champions of the Malaysia Super League with an unbeaten home record.

In July 2013, Hariss Harun rejected the offer of a contract from the Portuguese Primeira Liga side, Rio Ave.[11] National Service commitments and salary issues were speculated as reasons why the deal broke down, despite the help of Singapore billionaire Peter Lim and agent Jorge Mendes.

Following Hariss' decision not to join Rio Ave, Malaysia Super League side Johor Darul Ta'zim moved quickly to confirm his signing in a two-year deal worth over US$20,000 (S$25,000) per month in November 2013.

He scored a header from a corner on the opening match day of the 2016 Malaysia Super League against Selangor FA which ended 1–1 with Johor Darul Ta'zim winning the 2016 Sultan Haji Ahmad Shah Cup on penalties (7–6).

[17] He had been training with CE L'Hospitalet, but the move was cancelled 2 weeks after Hariss arrived in Spain due to a taxation problem for the Spanish side, resulting in them being unable to register new players.

During the 2024–25 AFC Champions League Two home fixture against Chinese club Zhejiang Professional on 19 September 2024, Hariss scored a volley from outside the box in the 44th minute to break the deadlock just before half time.

Hariss was scouted by then-national team coach Radojko Avramović who gave him his international debut in a friendly against North Korea on 24 June 2007 when he came on as a 70th-minute substitute.

On 13 June 2017, Hariss captained Singapore during the FAS 125th anniversary friendly match against two time FIFA World Cup champions Argentina where he almost scored a goal from a set piece.

Hariss scored his 7th international goal in a 2–0 friendly victory over Fiji, helping new head coach Fandi Ahmad to his first win.

[38] On 7 November 2021, Hariss tested positive for COVID-19, just one day before the national team is flew to Dubai for a training camp in preparation for the 2020 AFF Championship.

[43] On 9 March 2014, Hariss married his girlfriend Syahirah Mohamad in a function hall opposite Jalan Besar Stadium, home ground of LionsXII.