On 19 June 2020, Popović made his official debut for Partizan in a 1–0 away loss at Vojvodina in the last round of the COVID-19-shortened 2019–20 Serbian SuperLiga.
[2] He would become the first-choice goalkeeper for the 2020–21 Serbian SuperLiga, mainly due to new league requirements for under-21 players, making 21 appearances in the process.
Upon the departure of Vladimir Stojković, Popović made his debut in European competitions on 29 July 2021, keeping a clean sheet and saving a penalty in a 2–0 away victory over Slovak club DAC Dunajská Streda in the UEFA Conference League.
[5][6] Aleksandar Popović officially left Partizan on July 28, 2023 and signed a contract with DAC Dunajská Streda.
The young goalkeeper signed a three-year contract with the new club, while Partizan received €210,000 from the transfer, plus certain percentages from the next sale.