The carnivorous marsupials have been released into a 400-hectare (988-acre) wildlife sanctuary north of Sydney, New South Wales, Australian NGO Aussie Ark said in a statement.
"In 100 years, we are going to be looking back at this day as the day that set in motion the ecological restoration of an entire country," said Tim Faulkner, president of Aussie Ark.
"Not only is this the reintroduction of one of Australia's beloved animals, but of an animal that will engineer the entire environment around it, restoring and rebalancing our forest ecology after centuries of devastation from introduced foxes and cats and other invasive predators."
Tasmanian devils died out on the mainland after the arrival of dingoes and were restricted to the island of Tasmania. However, their numbers suffered another blow from a contagious form of cancer known as Devil Facial Tumor Disease (DFTD), which has killed around 90% of the population since it was discovered in 1996.