[3] On 25 May 2014, he made his professional debut with OFK Beograd under coach Zlatko Krmpotić in a 4–2 loss against Red Star Belgrade.
[5] Stefan signed with Australian A-League side Central Coast Mariners in December 2020.
[6] His first and only competitive appearance for the Mariners came as a late substitute in a 3–2 win over Melbourne City in the 2020–21 A-League on 3 February 2021.
[7] In September 2021, Janković signed for Maltese Challenge League side Pembroke Athleta.
[8] He made his debut for the side in their opening game of the 2021–22 Maltese Challenge League against Vittoriosa Stars.