Walkup played college basketball for Stephen F. Austin State University, before being named Southland Conference Player of the Year for two consecutive seasons (2015 and 2016).

[3][4] In November 2010, Walkup committed to play college basketball at Stephen F. Austin State University for the Lumberjacks.

"[5] His father commented on Walkup's recruitment, "I'm sure scouts looked at him and said, 'Well, he's a 6–4 white guy and he can't shoot and he plays the four.

'"[6] Walkup immediately assumed a big role with the Lumberjacks as the team's sixth man during his freshman season.

That season, the Lumberjacks won a school-record 27 games, winning their third Southland Conference title of all-time and qualifying for the National Invitation Tournament (NIT).

His teammates began referring to him as "The Snake", after establishing his ability for rebounds, consistently drawing fouls for opposing players, and providing scrappy defense for the Lumberjacks.

[10] On October 30, he was acquired by the Windy City Bulls of the NBA Development League as an affiliate player of Chicago.

On April 18, 2023, Walkup received Greek citizenship through honorary naturalization, which was signed by the Minister of the Interior, Makis Voridis, and the President of Greece, Katerina Sakellaropoulou.

[6] Walkup claimed that he had been asked to shave it, but he felt that it fit in with Stephen F. Austin's mascot, the Lumberjacks.