He spent several years coaching Brighton & Hove Albion's under-21s and made his first-team managerial debut with Swindon Town in 2015.

[6] At age 19, he suffered a knee injury and failed to win a contract with Leyton Orient, so he decided to focus on coaching.

[8][5] Williams's side were the first Brighton team to play at the club's Amex Stadium, which opened in 2011, as they beat Eastbourne Borough in the Sussex Senior Challenge Cup final.

[9] In 2013, Williams was appointed assistant manager to Mark Cooper at League One club Swindon Town, and helped the team reach the 2015 play-offs before losing to Preston North End in the final.

[13] In November 2016, Tim Sherwood was named the club's director of football and began coaching the team alongside Williams.

[3][26] County scored 117 goals throughout the campaign and set a new club record unbeaten run in the league of 25 games.

[29][30] Williams left County in January 2024, with the club fifth in the league and having scored 55 goals, the highest across England's top four divisions.

[31] On 5 January 2024, Williams returned to Championship club Swansea City as head coach on a three-and-a-half-year contract, replacing Michael Duff mid-season.

[32][33][9] Williams took charge of his first match the following day, a 2–0 victory against Morecambe in the FA Cup, with goals from Arsenal loanee Charlie Patino and striker Jerry Yates.