Born in Sydney, he attended Catholic schools before becoming an engine-driver and official of the Australian Federated Union of Locomotive Enginemen.

However, in 1941 John Curtin reunited the party, and Sheehan and the other Lang Labor members rejoined the federal ALP.

On Tuesday 19 April 1955, the Prime Minister, Sir Robert Menzies, in his House of Representatives speech, paid tribute to the recently deceased Sheehan, crediting him with having "possessed the most remarkable charm and generosity."

Menzies went further to illustrate that Mr Sheehan who had sat in the House for eighteen years "[had] no enemies."

ALP leader H. V. Evatt described Sheehan, on the same occasion, as "kindness itself to new members."