Gudelj signed his first professional contract with NAC Breda in July 2009 but failed to make an official appearance in his debut season despite being named on the bench several times.

[2] In the summer of 2013 Gudelj transferred to AZ Alkmaar for a fee of around €3 million, sold by his father who was manager at NAC, signing a four-year contract.

[9] On 14 March, he scored his first goal for the club in the fourth group stage match of the AFC Champions League against Jeju United, which ensured Guangzhou Evergrande's 2–0 away win.

[14] Having represented Serbia at the U19 and U21 levels, Gudelj debuted for the senior squad on 5 March 2014 in a 2–1 away victory against the Republic of Ireland in a friendly match after coming on as a last minute substitute for Antonio Rukavina.

[20] Gudelj was part of the Serbia squad for UEFA Euro 2024 and started the team's opening match of the tournament against England, playing the first half of the 1–0 loss before being substituted for Ivan Ilić.