Foreign Minister Penny Wong confirmed that all hostages had been safely released.
“I welcome news from PNG that all hostages have been released and will soon be reunited with their families,” she said on Twitter.
The academic, Professor Bryce Barker, and the other hostages were reportedly held at gunpoint by 20 armed men, according to a PNG police incident report.
Barker is a New Zealand national, but he is based at the University of Southern Queensland.
The highly regarded and experienced archaeologist and his research crew were conducting fieldwork in the remote Southern Highlands province of PNG when they were taken hostage by the armed group.
PNG authorities confirmed the release of one hostage on Friday.
The final three hostages – the professor and two PNG women – have now been freed safely.
PNG Prime Minister James Marape said the final three hostages were secured “through covert operations” without paying the $3.5 million kina ($A1.4 million) ransom.
“To criminals, there is no profit in crime,” he wrote on Facebook.
He thanked all officials involved in the operation.
The vice-chancellor of the University of Southern Queensland expressed relief and thanked the PNG, Australian and New Zealand governments.
“We are relieved to hear that our much-loved colleague from the University of Southern Queensland Professor Bryce Barker has been released today,” Geraldine Mackenzie said in a statement on Sunday.
She described Barker as a valued colleague who had many years’ experience undertaking research in PNG.
“Our deepest thanks go to the governments of Papua New Guinea, Australia and New Zealand, and the many people who worked tirelessly during this extremely difficult and sensitive time to secure their release,” Mackenzie said.
Wong thanked the PNG’s government for its leadership in securing a safe and peaceful resolution.
“Also thanks to the Australian and NZ officials who helped support this outcome,” she said.
A New Zealand Ministry of Foreign Affairs and Trade spokeswoman also thanked the PNG government for its leadership in securing the hostages’ release.
“We are extremely pleased that the hostage situation is resolved and we are relieved for the hostages and their whānau (family),” she said.