As a Liberal and Nationalist member of the House of Representatives, he became a protégé of Prime Minister Billy Hughes and was groomed as his successor.

He served as Minister for Trade and Customs (1919–1921), Defence (1921–1923), and Health (1921–1923), but his prime ministerial aspirations were brought to an abrupt halt by his defeat at the 1922 federal election.

Massy-Greene subsequently served two terms as a Senator for New South Wales (1923–1925, 1926–1938), but never regained his earlier influence in politics.

Walter Massy Greene was born on 6 November 1874 in Camberwell, Surrey, England (now part of South London).

In 1895, Greene joined the Bank of New South Wales and was posted to the gold-rush town of Kalgoorlie, Western Australia.

[1] In the fourth Hughes Ministry Massy-Greene was an Honorary Minister in charge of matters relating to price-fixing (27 March 1918 – 17 January 1919).

In a letter to Nationalist leader John Latham he stated "I have no desire to continue a membership with a party whose policy does not appeal to me; to be ground between the upper and nether millstone of a machine operated in the manner which appears acceptable to those who now control it".

[5] After leaving the Nationalists, Massy-Greene joined the provisional committee of Hughes' new Australian Party on 5 December 1929, with he and Duncan its only representatives in the Senate.

On 13 November 1952, he was admitted to Freemasons Hospital, Melbourne, where he underwent an operation on his gall bladder the following day.

[9] A state funeral was held at St John's Anglican Church, Toorak, before a cremation at Springvale Botanical Cemetery.