He played four years of college basketball in the United States, two for the Fordham Rams and two for the MSU Denver Roadrunners.
[5] Williamson played his last two years for the MSU Denver Roadrunners in the NCAA Division II.
In the opening round of the season, he scored 46 points with nine 3-pointers alongside 13 rebounds and seven steals against the Gladstone Port City Power.
[17] In 2008, Williamson played for the Hornsby Spiders in the Waratah League, averaging 18.5 points, 6.8 rebounds, 3.6 assists, 1.1 steals and 1.3 blocks in 10 games.
[6][18] In 2009, Williamson played for the Brisbane Spartans of the South East Australian Basketball League (SEABL).
[6] In 2011, Williamson played for the East Perth Eagles of the State Basketball League (SBL).
[20] Initially joining the Eagles out of convenience while still in the NBL, he decided to continue to play for the club post his professional career.