Hackett took up journalism and contributed to the Sydney Morning Herald, but in 1876 went to Melbourne to become vice-principal and tutor in law, logic and political economy, at Trinity College.

In 1880 he was a candidate for Normanby at an election for the Victorian Legislative Assembly as an advanced liberal, but was badly defeated and lost his deposit.

[citation needed] In 1894, Hackett was elected to the Legislative Council as representative of the south-western province, and held this seat until his death.

He also strongly supported Forrest in his development policy, in the building of the pipe line to the goldfields, and the making of Fremantle harbour.

He was a prominent member of the Church of England, holding the offices of registrar of the Diocese of Perth and chancellor of St George's Cathedral.

[citation needed] The University of Western Australia opened in 1913 with Sir John as its first chancellor, and he gave it its first substantial private contribution when he endowed the chair of agriculture.

He took a trip to the eastern states which appeared to have benefited him; however he died suddenly on 19 February 1916 of a heart condition and was buried in Karrakatta Cemetery.

This was an unexpectedly large sum, because by the time that the university was ready to receive it in 1926, shares in The West Australian had increased greatly in value.

[citation needed] The species epithet of the extinct giant echidna Murrayglossus hacketti honours Hackett.