The Government has bought seven hectares of kahikatea forest on the Wairarapa Plains for $340,000.
The money has come from the Nature Heritage Fund established in 1990 to protect the country's indigenous ecosystems.
The forest area, known as Allen's Bush, is next to the Lowes Bush Scenic Reserve which was purchased by the Fund in 2000.
Conservation Minister Nick Smith says the forest is home to a number of species uncommon elsewhere in the Wellington region.
He says the purchase completes the protection of the largest and most intact area of kahikatea swamp forest in the region.