The Governor General, Sir Peter Cosgrove, has rubber-stamped Malcolm Turnbull's new leadership team, making yesterday's cabinet reshuffle official.
Nationals leader Barnaby Joyce was sworn in as the country's new Infrastructure minister.
Hours earlier, Mr Joyce was fending off questions over his decision to demote Nationals colleague Darren Chester and take over his infrastructure portfolio.
"Darren has a huge future in front of him. He understands," Mr Joyce told reporters at Parliament House on Wednesday morning.
"We've all played sport. We've all had the times where we've played first grade, then played second grade, then played first grade again."
On Tuesday, Mr Chester said while he was "disappointed", he looked forward to many more years in the parliament. He said he would be a "very active backbencher" and focus on his local electorate of Gippsland.
Mr Joyce said the decision to dump his Victorian colleague from cabinet was designed to make way for more Queenslanders, and ensure Nationals from every region were well represented in the cabinet.
Nationals deputy Bridget McKenzie is now a cabinet minister, taking over responsibility for sport, rural health and regional communications.
Peter Dutton will lead the new Home Affairs portfolio, which will take responsibility for Australia's intelligence agencies, national security and immigration.
The new ministry, modelled off the UK's Home Office, will oversee the domestic spy agency ASIO and the Australian Federal Police. Mr Dutton's former Immigration ministry will be run out of the same office.
There will be two more junior ministers beneath Mr Dutton.
Angus Taylor will be Minister for Law Enforcement and Cyber Security, while Alan Tudge will become Minister for Citizenship and Multicultural Affairs.
Finance Minister Mathias Cormann is also now the special minister of state.
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The prime minister added several fresh faces to his ministry on Tuesday, in what is expected to be the last cabinet shake-up before the 2019 election.
He promoted West Australian Christian Porter to Attorney-General, after George Brandis was recommended to take over as UK High Commissioner in the new year.
First-term MP David Littleproud takes over Mr Joyce's old Agriculture portfolio, while his colleague John McVeigh deals with regional development and local government.
Michaelia Cash, previously the minister for Employment, has been given a new title as Minister for Jobs and Innovation.
Arthur Sinodinos is missing from the ministry, after he informed Mr Turnbull his cancer treatment was taking longer than anticipated.
- with AAP
