Trafford signed a one-year contract with the Vancouver Whitecaps in June 2008, after finishing his fall semester at UNLV. He went on to play 14 games in the USL First Division in 2008, and was re-signed by the Whitecaps on December 3, 2008 for the 2009 season. Trafford played 23 games in 2009 as the team again reached the USL Championship game, eventually losing out to the Montreal Impact. Trafford played a variety of roles for the Vancouver Whitecaps.
In an effort to develop at one position, he signed with Real Maryland Monarchs under coach Anthony Hudson to be the club's left sided central defender. Trafford would go on to score two goals and played every minute during the club's 2010 campaign that ended in August 2010, allowing him to transition to a European club.
Mariehamn
On August 29, 2010, after impressing on trial, Trafford signed a 6-month contract with a 2-year option with Finnish club IFK Mariehamn. IFK Mariehamn picked up the option after Trafford played all seven matches to conclude the 2010 season. Mason would go on to play every match available throughout his IFK Mariehamn career.
Traffored rejected a new contract with IFK Mariehamn in order to test the free agency market. Trafford considered offers from Sweden, Finland and North America and participated in his first Canadian National Team camp in Phoenix, Arizona and Houston, Texas with friendlies against Denmark and the United States. Immediately after, he went on trial with the Seattle Sounders for a week but could not play in a friendly match against the Portland Timbers due to having food poisoningthe night prior, along with several other teammates. He then elected to go on trial in China where he was once again successful. On February 23, 2013, Trafford signed with China League One club Guizhou Zhicheng for 1 year as one of the club's three international players.
Ottawa Fury
On March 17, 2014, Trafford signed with North American Soccer League expansion club Ottawa Fury FC. In the club's first professional season, Trafford played a key role at centre-back, appearing in all 29 of the Fury's matches in all competitions and earning himself the club's Supporters' Player of the Year award. In the 2015 season, the club's acquisition of centre-backs Colin Falvey and Rafael Alves pushed Trafford out of the starting lineup for much of the Spring season, however after discussions with management he was given an opportunity to play at left-back, a position he had played previously at IFK Mariehamn. Trafford was very successful and helped start a remarkable and record-breaking defensive run by the Fury during which they lost only one match and conceded by far the fewest goals of any club in the league, earning the club the NASL Fall Championship title and its first-ever berth in the Soccer Bowl playoffs. At the end of the season, Trafford once again earned the Fury Supporters' Player of the Year award.
On October 1, 2015, Trafford signed a contract extension with Ottawa through 2017. However on February 4, 2016, a clause in Trafford's contract requiring the club to transfer him if a certain minimum fee was met was activated by expansion club Miami FC, sending him instead to his birthplace of Florida for the 2016 season. At the time of his departure, he was the Fury's all-time appearance leader.
Cavalry FC
On February 27, 2019 Trafford signed with Canadian Premier League club Cavalry FC. In November 2019, Cavalry would confirm that Trafford would return for the 2020 season.
International career
On January 18, 2013, Trafford received his first call up by the Canadian national team for friendlies against Denmark and United States He made his senior team debut on January 26 in a friendly against Denmark as a second half sub for Tosaint Ricketts, the game ended as a 4-0 defeat.
Personal life
His cousin Charlie Trafford is also a professional soccer player with Inverness Caledonian Thistle in Scotland. In 2013, Mason arranged for Charlie to sign for his former club IFK Mariehamn.
