"[5] He made his official debut against Finnish club HJK on 30 July 2014, in APOEL's 2–2 away draw for the third qualifying round of the 2014–15 UEFA Champions League.

[6] On 5 November 2014, aged 18, he made his first UEFA Champions League group stage appearance, playing the full 90 minutes in APOEL's 0–1 defeat against Paris Saint-Germain at Parc des Princes.

[7] In his first season at APOEL, Ioannou appeared only in seven matches in all competitions, but he managed to win the double, as his team won both the Cypriot championship and the cup.

[11] On 25 September 2020, Ioannou returned to England, joining EFL Championship side Nottingham Forest for an undisclosed fee.

[14] On 5 July 2021, it was announced Ioannou had joined Serie B side Como on a season-long loan deal.

[5] He made his Cyprus U21 debut on 5 September 2014, coming on as a 70th-minute substitute in a UEFA European U-21 Championship qualifying match against Belgium.