His first appearance for the Pars came as a substitute against Arbroath in August 2013,[4] and in November of that year he made his full first team debut in a 3–1 home win against Brechin City.
After first dislocating his kneecap[6] against Stirling Albion[7] which forced him out until the end of February 2015, he then fractured his leg against Forfar Athletic in August 2015.
[10] Shortly after leaving Dunfermline, Williamson signed a two-year deal with fellow Scottish Championship side Partick Thistle.
[12] Williamson won the second honour of his career helping Thistle win the 2020–21 Scottish League One title.
[17] After an impressive start to the 2017–18 season, Williamson was called up to Scot Gemmill's Scotland U21 squad to face England and Latvia in October 2017.