Williamson helped Lower Merion High School to win the PIAA state title in 2006.
[3][4] He scored a career-high 20 points in his senior season, as St. Joseph's lost 75–67 to Temple in overtime.
[6] Source:[3] Following his graduation from college, Williamson signed his first professional contract with the Austin Toros.
[14] On 9 September 2015, Williamson returned to the London Lightning under new head coach Kyle Julius.
[17] Williamson averaged 7.5 points, 7.7 rebounds, and 1.5 assists per game during the 2019–20 season, earning All Canadian Second Team honors.
[18] Williamson holds dual American-Canadian citizenship, since his mother was born in Toronto.