Kouassi played for the Ivorian football club Moossou youth team before going abroad to have trials with TSG 1899 Hoffenheim, Club Brugge and Monaco before having a successful trial with Croatian club Hajduk Split who offered him a three-year contract in January 2013.
Hajduk Split
Kouassi made his debut for Hajduk Split in a league game against Slaven Belupo on 16 February 2013 that ended in a 2–0 victory.[2] He gradually started to establish himself within the team and on 21 April 2013, Kouassi scored in a draw against Slaven Belupo, marking the 4000th jubilee championship goal for Hajduk Split.[3] He further endeared himself towards the fans when he scored and assisted for a goal against Lokomotiva in the 2012–13 Croatian Cup final, which the club won 5–4 on aggregate.[4]
Shanghai SIPG
Chinese Super League club Shanghai SIPG announced that Kouassi had joined the squad on 25 February 2015 and signed a contract until 2017.[5] He made his debut in a league game on 7 March 2015 against Jiangsu Guoxin-Sainty in a league match that ended in a 2–1 victory.[6] Kouassi scored his first goal for the club where he also registered an assist in a 2–1 win over Chongqing Lifan.
On 10 December 2021, Kouassi joined Turkish Süper Lig side Trabzonspor on a three-and-a-half-year contract.[9] He scored on his debut for the club on 9 February 2022 during the 2021–22 Turkish Cup where he scored the winner in a 2–1 win against Denizlispor which send the team to the quarter-finals. Kouassi also helped the club to win the 2021–22 Süper Lig title. He also help Trabzonspor to win the 2022 Turkish Super Cup after thrashing Sivasspor 4–0 on 30 July.
Fatih Karagümrük (loan)
On 6 September 2022, he was loaned to Fatih Karagümrük.[10] He scored his first goal for the club in a 5–4 lost to Fenerbahçe on 9 October.
Zhejiang Professional
On 22 January 2023, Kouassi returned to China to join top tier club Zhejiang Professional signing a deal until 2025.[11] He make his debut for the club on 15 April in a 2–0 lost to Changchun Yatai. Kouassi scored his first league goal on 2 June in a 3–0 win over Shenzhen. He make his AFC Champions League debut on 20 September in a 4–1 away lost to Thailand club Buriram United.
In a league match against Tianjin Jinmen Tiger on 19 April 2024, Kouassi recorded a brace of assist helping his team defeat their opponent 3–2. He then recorded another brace of assist on 30 April in a 4–1 win over Henan. During the 2024–25 AFC Champions League Two group stage match against Indonesian club Persib Bandung on 3 October at home, he scored the only goal in the match which help his team to gain 3 points in the group.
International career
Youth
Kouassi was named in the Ivorian squad for the 2011 African U-17 Championship. He scored in the game against Gambia on 15 January 2011.[12]
He was also named in the Ivorian squad for the 2011 FIFA U-17 World Cup. He played in all four games before the Ivorians were eliminated from the competition by France in the round of 16.[1]