Originally the reserve covered only the core forested section of the currently designated area, and was named Abernethy Forest NNR. The Dell Woods section was added 1988, forming a 375 hectare extension to the existing NNR. In 2007, the NNR was greatly extended, becoming the new Abernethy National Nature Reserve, which extends from Abernethy Forest itself up into high Cairngorms, taking in Loch A'an and the mountains of Bynack More, Beinn Mheadhoin and the southern side of Cairn Gorm. The Abernethy NNR is classified as a Category II protected area by the International Union for Conservation of Nature.