Dempster appeared for the County scratch sides during the war but left the staff when the war ended. He played three times for Warwickshire in 1946 before returning to New Zealand to become a coach. He was selected to play for New Zealand in a one-off Test in Christchurch against England in March 1947, but withdrew due to an eye injury four days before the match. The match ended in a draw. Dempster made his final appearance for Wellington against Auckland at Eden Park in January 1948 scoring 7 and 41.