|Date of birth||24 November 1989|
|Place of birth||Greenock, Scotland|
|Height||1.88 m (6 ft 2 in)|
|2010||→ Largs Thistle (loan)||8||(0)|
|2012||→ East Stirlingshire (loan)||5||(0)|
* Senior club appearances and goals counted for the domestic league only and correct as of 21:31, 11 January 2016 (UTC).
Born in Greenock, McWilliams began his career at Greenock Morton. He worked his way through the youth system to the Under-19s and then was called up to the first team. On 15 August 2009, he made his professional debut in a game against Dunfermline Athletic.
After being released by Morton, on 30 July 2010, Ryan signed for Ayr United on a 1-year deal as back up to David Crawford. At the end of the 2010–11 season, McWilliams signed a one-year extension with Ayr, but left at the end of the 2011–12 season.
McWilliams signed a one-year contract with the Second Division outfit Albion Rovers, then immediately after Rovers played against Morton in the Challenge Cup he was loaned out to East Stirlingshire on a 6-month deal, with his first game ironically to be against Morton. He asked to be released from his contract with Rovers in January 2013, after falling to third choice at the club.
East Stirlingshire traveled to play Rangers on 18 August 2012, where McWilliams earned the Man of the Match award after several point blank and double saves; these helped keep the score respectable as the Shire lost 5-1. He was recalled by Albion after an injury to Chris McCluskey.
McWilliams also coached the goalkeepers at youth level for Morton.
- "Morton 0-2 Dunfermline Athletic". BBC Sport. 15 August 2009. Retrieved 15 August 2009.
- "Player News". gmfc.net. 26 March 2010. Retrieved 26 March 2010.
- "Elgin v Ayr". BBC Sport. 30 July 2010. Retrieved 31 July 2010.
- "Scottish Division Two ins and outs". BBC Sport (BBC). 7 August 2012. Retrieved 7 August 2012.
- "Rovers release McWilliams". Scottish Football League. 22 January 2013. Retrieved 22 January 2013.
- "McWilliams returns to Rovers". Scottish Football League. 31 August 2012. Retrieved 31 August 2012.
- "Morton's past, present and future under Hawke's eye". Scottish Football League. 9 December 2012. Retrieved 10 December 2012.
- Pews, Gary (30 March 2015). "REPORT: Port Glasgow 0 Blantyre Vics 1". Greenock Telegraph. Retrieved 6 May 2015.