He played for the New Zealand national cricket team in five Test matches as a wicket-keeper between October 1955 and February 1956, scoring seven runs in seven innings.
Mooney retired after the 1954–55 Plunket Shield season, and McMahon returned to the side for Wellington's match against the touring MCC.
He was selected for the tour of Pakistan and India in 1955–56, where he and his fellow wicket-keeper Eric Petrie each played four of the eight Tests.
[3] McMahon married a nurse, D. I. Perry, in Wellington in January 1956, immediately after returning from the tour of Pakistan and India.
[6] Following the death of John Richard Reid on 14 October 2020, McMahon became the oldest surviving New Zealand Test cricketer.