[3] A goalkeeper, Mathieson began his career in Scotland with junior clubs Dubbleside Hearts and Colinsburgh United.
[3] He was one of a number of former Middlesbrough players recruited by Bees manager Harry Curtis in the early 1930s and he linked up with former teammates Jack Holliday, Billy Scott, Herbert Watson and Ernie Muttitt at Griffin Park.
[3] Mathieson went straight into the team and was an ever-present during the 1934–35 season, helping Brentford to the Second Division title and promotion to the top-flight for the first time in the club's history.
[9] Mathieson lost his place in goal to another Scot, Joe Crozier,[9] during the 1937–38 season and departed the club at the end of the campaign.
[3] Things went well for Mathieson during the 1938–39 season at Queens, with the club finishing in sixth position and reaching the quarter-finals of the Scottish Cup.