 Mathews joined the Labor Party in 1956 and served as chief of staff to Prime Minister Gough Whitlam and Labor leaders in the Parliament of Victoria before entering politics.From 1972 to 1975, Mathews was the Federal Member for Casey, where he served as the Chairman of the House of Representatives Select Committee on Specific Learning Difficulties (1974–1975), and the Chairman of the Government Members' Committee on Urban and Regional Development.From 1979 to 1992, Mathews served as the State Member for Oakleigh in the Victorian Legislative Assembly during the Cain Government.