After working for the South Australian Government from 1998 to 2000 and the state Agent-General in London from 2000 to 2002, he held a variety of roles in high-profile law and accounting firms.

[1][3] Williams entered federal parliament at the 2013 election where he won the seat of Hindmarsh with a 1.89 percent margin from a 7.97 percent two-party-preferred swing, defeating Australian Labor Party incumbent Steve Georganas.

During the 2013 election campaign Williams committed to opposing any changes to the existing evening aircraft flight curfew at Adelaide Airport, centrally-located in the Hindmarsh electorate.

[5] In 2015 it was reported that Liberal insiders were considering Williams to be the preselected Liberal candidate for the safe state seat of Morphett if he failed to retain Hindmarsh at the 2016 federal election.

[6] When the preselection contest took place in April 2017, there was a dead-heat between Williams and Stephen Patterson, followed by a random ballot won by Patterson, who went on to successfully challenge the incumbent Liberal member, Duncan McFetridge.