Koulouris began his career with PAOK, and spent time on loan at Cypriot First Division club Anorthosis and at Atromitos, with whom he was top scorer in the 2018–19 Super League.

[2] He began his football career in PAOK's youth system as a young boy and came through the ranks, winning titles at under-17 and under-20 levels.

[4] On 28 October, he scored six times as Anorthosis beat Second Division opponents Elpida Xylofagou 9–0 in the Cypriot Cup.

[5] His first league goal came four days later: having entered the match away to Pafos as an 88th-minute substitute, he scored with a header that secured a 2–1 win.

[18] On 25 November, he scored from the rebound after Azer Bušuladžić's shot was parried to give Atromitos the lead at home to Olympiacos, but they went on to lose 2–1.

[29] On 22 June 2021, only a few hours after he got released by Toulouse, he return to his previous club Atromitos, having signed a two-year contract.

[33] On 28 February 2022, he scored a brace sealing a vital 2-0 away win against Apollon Smyrnis in his club effort to avoid relegation.

[35] On 5 July 2022, LASK officially announced the signing of Koulouris on a three-year contract, for a fee over €1,000,000 plus bonuses, making him the most profitable sale of Atromitos.

[36] He made his competitive debut for the club on the first matchday of the 2022–23 season, coming on as a substitute in the 61st minute for goalscorer Marin Ljubičić in a 3–1 home win against Austria Klagenfurt.

[37] After returning from a loan spell at Turkish club Alanyaspor, on 1 July 2023 Koulouris joined Polish Ekstraklasa side Pogoń Szczecin on a three-year contract.