He played two seasons of college basketball for the Hawaii Rainbow Warriors where he was named the Big West Conference Player of the Year in 2016.

[2] Stefan came to Mississauga with experience only as a soccer player, but a basketball court was located near his house in Canada.

Stefan spent most of his time taking care of his younger brother at their apartment, while his parents were busy.

For the following year, he transferred to The Kiski School in Saltsburg, Pennsylvania, where he averaged 17 points and eight rebounds in his sophomore season.

Other options he was considering included Louisville, Northwestern, Miami, Penn State, West Virginia, and Xavier.

“This was a tough decision for me, and Missouri will always hold a special place in my heart, but this was about having the opportunity to find a better fit where I could play a larger role on the court.

I am looking forward to my next opportunity and want to wish everyone at Mizzou all the best this year.”[5] In his junior year at Hawaii, Janković averaged 15.7 points, 6.8 rebounds and 1.3 blocked shots per game.

[9] On November 1, 2016, he was acquired by the Sioux Falls Skyforce of the NBA Development League as an affiliate player of the Heat.

However, Crvena zvezda came up short to defending the title in the ABA League, as they lost in the final series to Budućnost Podgorica.

[22][23] On May 2, 2023, Janković signed with Vancouver Bandits of the Canadian Elite Basketball League,[24] but he never played any games for them.

On August 23, 2024, Janković signed a testing player contract with Formosa Dreamers of the Taiwan Professional Basketball League (TPBL), his second stint with the franchise.

Currently he hasn't committed to any national team as he stated he was undecided and still considering representing either Serbia or Canada.