Born in Kettering, Northamptonshire,[1] Dempster began his career playing in the Football League for Rushden & Diamonds.

In May 2012, Dempster was released by Crawley after being deemed surplus to requirements[3] following a handful of League 2 appearances that year and a loan spell at Conference Premier club Mansfield Town.

After an injury and a spell on loan at Tamworth, Dempster established himself as a regular in the side that went on to win the Conference Premier on the last day of the season.

[11] On 7 February 2020, Dempster was appointed as Coventry City's Lead Professional Development Phase Coach, which saw him take charge of the club's under-18 team.

[12] On 2 August 2022, Dempster was appointed as Coventry City's Senior Professional Development Phase Coach, which saw him take charge of the club's under-21 team.