At international level, Šaponjić won the gold medal for Serbia at the 2015 FIFA U-20 World Cup, scoring two goals in the process.

He made his senior debut for the club in a league game on 30 November 2013, coming on as a 76th-minute substitute in a 2–0 home win over Spartak Subotica.

[4] He scored his first international goal for Partizan with an overhead kick in a 2–1 home win over BATE Borisov in the return leg of the Champions League play-off round on 26 August 2015.

On 11 July 2019, Šaponjić signed a three-year contract with Atlético Madrid for an undisclosed fee, reported to be in region of 500 thousand euros.

[17] He was the team's joint top scorer (alongside Nemanja Maksimović, Staniša Mandić and Andrija Živković) with two goals, as Serbia eventually won the tournament.