In 1885 he was elected M.P. for the Rhondda division, the first miners’ representative from South Wales; he represented Rhondda West, 1918-22. He was associated with the radical wing of the Liberal Party until 1906 when the Labour Party became a separate political organization, although the Miners’ Federation did not become affiliated until 1909.

Mabon, however, did not take an active part in political life; his main importance lies in the history of trade unionism in Wales. The miners were at first loosely organized in a number of small and independent local bodies. Mabon strove to preserve their autonomy despite the urge of younger miners to form a more unified and firmly-knit organization. They were successful, and in 1898 the South Wales Miners' Federation was formed, and Mabon became its first president. He tried to exert a moderating and conciliating influence on his followers, but could not prevent the series of critical disputes which produced the first general miners’ strike in 1912.

His other great interest was the eisteddfod. His burly appearance and powerful voice were features which made him well known and effective as a conductor of eisteddfodau at the end of the 19th and the beginning of the 20th cent., a period during which the eisteddfod attracted enormous crowds. He would often sing to the audiences, as he was endowed with a good tenor voice.

In 1860 he m. Sarah, daughter of Thomas Williams; she d. in 1900, having borne him three sons and three daughters.

Mabon was made a Privy Councillor in 1911. He d. at Pentre, Rhondda, 14 May 1922.