Easington-born Middlemas played for Herrington Swifts and Blyth Spartans before joining Hull City in March 1922. After making 10 league appearances for Hull, he joined York City in the summer of 1923. He made his debut for the club in the first game of the 1923-1924 season against Scunthorpe United in the Midland League.
He was awarded a testimonial match against Middlesbrough in April 1929, which earned him £111.
He left the club in July 1929 prior to York"s first season in the Football League. He made a total of 259 appearances and scored five goals for the club
He then returned to Blyth Spartans.