Joining the Auditor-General's Department, he was appointed Auditor General on 13 August 2000, succeeding S. M. Sabry, and held the office until his retirement from public service on 23 October 2006. He was succeeded by P. A. Pematilaka.[4]
He was listed by the Janatha Vimukthi Peramuna as a national list candidate at the 2015 general election.[5] Following the election Mayadunne was appointed to Parliament as a national list Member of Parliament taking oaths on 1 September 2015, however he resigned two days later on 3 September 2015.[1]