In May 2022, he was reported to be a contender for the vacant management position at AFC Wimbledon. On 24 February 2023, Dagenham parted company with McMahon with the side sitting in tenth position, five points off of the play-offs.
McMahon was considered a top contender for the AFC Wimbledon management job in May 2022. However, on February 24, 2023, Dagenham and Redovre decided to part company with him, leaving the team in tenth position, just five points away from securing a playoff spot.