Born in Varaždin, Ivanušec made his professional debut for Lokomotiva in the Prva HNL on 20 December 2015 against Slaven Belupo.

[11] In Mamić's system, Ivanušec simultaneously played as a right winger and an attacking midfielder, switching between the two positions with Lovro Majer during matches.

[15][16][17] A week later, he provided an assist to an extra-time winner by Mislav Oršić, which completed a 3–0 victory over Tottenham Hotspur and secured qualification to the Europa League quarter-finals.

[18] On 25 July 2023, Ivanušec scored a hat-trick in a 4–0 win over Astana in the first leg of the Champions League second qualifying round.

[25][26] In the final group game, the 2–1 loss to England on 31 March, Ivanušec made his 27th appearance for the team, becoming its most capped player in history.

[29] Ivanušec debuted for the Croatian senior squad on 11 January 2017 against Chile in the 2017 China Cup, coming on as a substitute for Franko Andrijašević at the 90th minute as Croatia lost the match on penalties 4–1.