The first eastern quolls in 50 years have been born in the wild on the Australian mainland, with the rice grain-sized pups offering hope to a species of marsupial devastated by foxes.

Eastern quolls - a furry carnivore that grows to about the size of a domestic cat - disappeared from the mainland in the 1960s but clung on in the island state of Tasmania.

Twenty of them were returned to their native environment in the Booderee National Park, south of Sydney, in March to see if they could survive and thrive.

It is the first time in Australia that a carnivore extinct on the mainland has been re-introduced to the wild and followed a 15-year project to bring feral predators in the area under control.

Booderee National Park Natural Resource Manager Nick Dexter said on Monday babies had been confirmed in three of the females' pouches.