Williams came through the youth ranks with Barnsley, playing over fifty first-team games. He made his debut on 5 October 2002, against Brentford.[2] On 22 March 2007, Williams joined Blackpool on loan until the end of the season.[2][3] He scored on his debut for the Seasiders, in a 3–1 win at Bradford City two days later.[4] Williams scored the first goal in the 2007 Football League One play-off final against Yeovil Town at Wembley Stadium.[5] The goal was part of a 2–0 win for Blackpool and saw them promoted to the Championship.[5]
Huddersfield Town
He was set to join Huddersfield Town in July 2007 before sustaining a hairline fracture to his shin.[6] The transfer was completed the following month, with Williams signing a three-year contract for an undisclosed fee.[7] He made his debut for the club in December at Leeds United, and scored his first goal against Brighton & Hove Albion in January 2008. He made 28 appearances during his first season with Huddersfield,[8] and 39 in the 2008–09 campaign. The following season, he played in both legs of the League One play-off semi-final defeat to Millwall. Williams was released in the summer of 2010 when his contract expired and spent time on trial at Aberdeen.[9]
Stockport County
Williams joined Stockport County in August 2010 on non-contract terms.[10][11] He signed a full-time contract at the end of the month,[11][12] and scored his first goal for the club against Barnet in October.[13] Williams made 25 appearances for Stockport before leaving for Rochdale in January 2011.[14]
Rochdale
Having joined Rochdale on a free transfer,[14] Williams made his debut in March against Notts County. He was released at the end of the season after the club decided against offering him a new contract.[15] He made nine appearances for Rochdale.[15]
Plymouth Argyle
Williams signed a one-year contract with Plymouth Argyle in July 2011.[16][17] He made his debut in a 1–1 draw at Shrewsbury Town in August,[18] and scored his first goal for the club in a 2–0 win against Macclesfield Town in September.[19] In his first season, Williams made 30 appearances in league and cup competition, scoring two goals.[20] Williams signed a new one-year contract in June 2012,[21][22] and began the new season with three goals in his first five appearances, against Oxford United, Burnley and Port Vale.[20] A stomach injury he sustained in October kept him out of the team for two months.[23] Williams left the club in January 2013 when his contract was cancelled by mutual consent.[23][24] In his two seasons with the club, Williams played in 42 league games, made four appearances in cup competitions and scored five goals.[20][25]
Limerick
In February 2013, Williams joined League of Ireland Premier Division club Limerick.[26][27] "We are delighted to get a player of Robbie's talent and experience on board," said manager Stuart Taylor.[26] Ahead of the new season, Williams said that "I'm not really familiar with the standard but the way people are talking it's looking positive."[28]
Williams made more appearances for the Shannonsiders than for any other club.
In January 2018, Williams signed for Galway United in the League of Ireland First Division.[30] Williams said, "It's a new challenge. I've been at Limerick for a good few years and Cork City last year. Shane Keegan rang me a few weeks back and I'm delighted to come down to help and hopefully we can fire the team up to where it belongs."[30] He made his league debut for The Tribesmen in their 4–1 win over Athlone Town on Friday, 23 February.[31]
Back to Limerick
Williams returned to Limerick FC, this time as a player coach and also a coach for the U19 squad.[32]