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 .