[2] Five months after signing for Rangers, Williamson broke his right leg while on a night out during an end of season tour of Australia.
[6] Kilmarnock finished highly in the Scottish Premier League and he guided them into Europe, playing a total of four two-legged ties over three seasons.
[6] Nonetheless, Hibs produced several excellent young players, including Scott Brown, Derek Riordan, Garry O'Connor, Kevin Thomson and Steven Whittaker.
After keeping the Pilgrims in the division in his first full campaign, a poor run of results at the start of the 2005–06 season led to his dismissal on 6 September 2005.
Financial constraints at Plymouth Argyle resulted in a number of signings which contributed to his demise, most notably Taribo West.
Williamson appeared as a pundit on BBC Radio Scotland's Sportsound before he was appointed as Chester City manager on 11 May 2007.
[11] Williamson's first Football League match in charge of Chester ended in a 0–0 draw with Chesterfield on 11 August 2007 and has established them as a promotion contender in the opening months of the season.
After mid-season, Chester's form began to drop rapidly, winning only 1 out of 14 games since Boxing Day; Williamson was sacked on 2 March 2008.
[13] Williamson replaced Csaba László, who resigned in July 2008 to join Scottish Premier League side Hearts.
[18][19] On 5 July 2013, it was announced that Williamson agreed terms with Kenyan Premier League side Gor Mahia to join the club as their new head coach.