Kouassi played for Académie Symbiose Foot d'Abobo in the Ivory Coast before moving to Armenian club Shirak in early 2014.[1] In the summer of 2014 he joined the youth system of Russian club Krasnodar.[1]
Krasnodar
In December 2015, Kouassi signed a new contract with Krasnodar.[2] Kouassi made his debut for Krasnodar on 21 May 2016, in a 1–0 victory against Amkar Perm in the Russian Premier League.[3] He became a regular the following season, 2016–17, playing in a total of 18 matches by the end of December 2016 and helping his side to fifth place in the league.[4] During this time, Kouassi also scored his first goal; opening the scoring in a 3–0 win over Maltese side Birkirkara in a UEFA Europa League tie on 4 August 2016.[5][6]
Celtic
On 3 January 2017, it was reported that Scottish Premiership club Celtic had agreed a transfer fee of around £3 million with Krasnodar to sign Eboue Kouassi.[7] Celtic announced the signing of Kouassi on a four-year-contract, subject to obtaining a visa, on 12 January 2017.[8]
Kouassi made 22 first-team appearances for Celtic in his first three years with the club. He was loaned to Belgian club Genk in January 2020.[9]
Genk
Kouassi signed for Genk on 1 July 2020, for €1.5 million.
Arouca
On 31 August 2021, Kouassi was loaned to Arouca.[10] On 7 July 2023, Arouca announced the free signing of Kouassi on a free transfer, with the player signing a two-year deal.[11]