The refugees -- three Iranians and one ethnic Rohingya from Myanmar -- were flown into Phnom Penh, the capital of one of Southeast Asia's poorest nations with a weak record for upholding human rights.
"They have arrived now, and we already handed them to the IOM," Chhay Bonna, the airport's chief immigration officer told AFP, referring to the International Organization for Migration which is tasked with helping the four settle into their new home.
The refugees, three men and one woman, were greeted by Cambodian immigration officials and representatives from Australia's embassy at the VIP section of Phnom Penh's airport, an AFP reporter on the scene said.
"They're here, they're healthy and we ask for privacy for them," IOM regional spokesman Joe Lowry told AFP.
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Under Canberra's hardline immigration policy, asylum-seekers who arrive by boat are denied resettlement in Australia and sent to Papua New Guinea and Nauru, even if they are genuine refugees.
The deal was inked last September to allow those granted refugee status in Nauru to permanently resettle in Cambodia.
Under the agreement Cambodia will accept Australia's unwanted refugees in return for millions of dollars of aid over the next four years. Canberra will cover all direct costs of the settlement arrangement.
Cambodia has also been criticised for its own record of helping refugees, including Vietnamese Montagnards who are often deported.
Rights groups hit out today at the move to ship the first set of refugees to Cambodia under the deal with Australia.
"Cambodia clearly has no will or capacity to integrate refugees permanently into Cambodian society," Phil Robertson, from Human Rights Watch said.
In a statement Amnesty International Australia said Cambodia's track record of protecting asylum-seekers was "poor" and called on Canberra to "cease the transfer of asylum seekers and refugees to third countries where they are not adequately protected from human rights abuses".