He was a follower of Henry George and an opponent of capital punishment and, from 1917 to 1920, served on Collingwood City Council.
In 1919, Kiernan was elected to the Victorian Legislative Council for Melbourne North Province.
His resignation from Cabinet over a union dispute concerning termination of the Premiers' Plan saw him expelled from the Labor Party in 1932, and he served thereafter as an independent member.
[3] After travelling to Italy in the early 1930s, he returned to Australia a committed supporter of Benito Mussolini.
Kiernan died in Fitzroy in 1967,[3] and is buried in the Catholic section of Melbourne General Cemetery, of which he was a trustee.