The purchase of land at Lake Innes, south-west of Port Macquarie was a joint initiative with $3.5 million in funding from Koala Conservation Australia.
As well as the koala, three additional threatened species — the eastern coastal free-tailed bat, glossy black cockatoo and grey-headed flying-fox — have been recorded in the 194 hectares.
The government will add the land to the adjacent Lake Innes Nature Reserve and protect it by declaring it an 'Asset of Intergenerational Significance'.
Member for Port Macquarie Leslie Williams said it was a victory for the many advocates in the local community who fought so hard for this result.
"Our community has the surety of knowing their children for generations to come will see koalas in the wild, which is cause for celebration," Ms Williams said.
Environment Minister Matt Kean said the sale would help the government reach its target of doubling the state's koala population by 2050.
"Our iconic koalas are increasingly threatened by the loss and fragmentation of habitat. This purchase will protect critical habitat from development and ensure the koala population in this area is safeguarded forever," Mr Kean said.
The World Wide Fund for Nature-Australia welcomed the decision.
"On top of deforestation for agriculture and native forest logging, clearing of koala homes for urban expansion is a major driver of koala declines on the NSW north coast," Dr Stuart Blanch, WWF-Australia conservation scientist.
"Expansion of the protected areas estate across different land tenures is critical to save koalas from extinction, as well as the hundreds of other species that also call koala forests home."