Beginning his senior career at St Johnstone, Mark made his professional debut whilst out on loan at Arbroath in 2010, where he went on to play nine times that season, scoring his first professional goal in a 3-2 win over Berwick. The following season he was out on loan again, firstly at Stranraer for a month, and then a five month spell at Elgin City, making 21 appearances in total.
After four years at McDiarmid Park, the then 19 year-old defender moved on to Queen of the South in July 2012. He quickly became a regular in the first team, winning the Second Division Championship and the Challenge Cup in his first season. Mark went on to make 125 appearances and scored 16 goals in his three seasons at Palmerston. Upon the expiration of his contract with Queen of the South, Mark signed for United on a three-year deal in June 2015.
Despite a tumultuous first season and changes in management, Mark featured regularly at the centre of defence during the 2016-17 campaign. He scored his first goal for the Club in a 3-2 defeat to Hearts, before adding to his tally twice more during the season, showing himself to be a continued threat from set pieces.