The reserve centre lies 11 km due south of Impendle town and about 50 km west of Pietermaritzburg. The terrain is undulating, steep and rocky at the highest points, and dissected by small river drainage lines that fall over a minor escarpment as they join the Umkomaas River, which forms much of the site's southern boundary. The altitude ranges from 935 to 1 586 m a.s.l. The site is predominantly grassland. Some of this was lost to agriculture, but more than 2 000 ha remain, most of which is Southern KwaZulu-Natal Moist Grassland, Drakensberg Foothill Moist Grassland and Midlands Mistbelt Grassland. In its pristine state, this grassland should be dominated by red grass Themeda triandra, but the scarcity of this grass indicates that the site has been man-modified in the past. Approximately 850 ha of Southern Mistbelt Forest are found in the reserve.
The vlei is very good for African Marsh Harrier Circus ranivorus, Grey Crowned Crane Balearica regulorum and Wattled Crane Bugeranus carunculatus. The surrounding rolling grassland holds six pairs of Blue Swallow Hirundo atrocaerulea. Blue Crane Anthropoides paradiseus, Denham's Bustard Neotis denhami, Southern Ground-Hornbill Bucorvus leadbeateri and Black-winged Lapwing Vanellus melanopterus also occur. A flock of Southern Bald Ibis Geronticus calvus is often present. The forest is home to Bush Blackcap Lioptilus nigricapillus, Orange Ground Thrush Zoothera gurneyi, Knysna Turaco Tauraco corythaix and Forest Canary Crithagra scotops. Other southern African endemics include Cape Grassbird Sphenoeacus afer, Drakensberg Prinia Prinia hypoxantha, Jackal Buzzard Buteo rufofuscus and Gurney's Sugarbird Promerops gurneyi.
Globally threatened species are Southern Bald Ibis, Blue Crane, Blue Swallow (3–4 breeding pairs and 20–30 individuals), Denham's Bustard, Grey Crowned Crane, Wattled Crane (one breeding pair and three individuals) and Bush Blackcap. Regionally threatened species are Orange Ground Thrush, Lanner Falcon Falco biarmicus and Cape Parrot Poicephalus robustus. Biome-restricted species that are commonly encountered are Knysna Turaco and Swee Waxbill Coccopygia melanotis.
The rare tree dassie Dendrohyrax arboreus is found in the forest. A number of rare plants that occur are Ocotea bullata, Curtisia dentata, Andrachne ovalis, Scilla natalensis, Encephalartos ghellinckii and Alepidea amatymbica.
Land claims have been lodged for certain sections of the reserve and fences along some boundaries are regularly cut. Invasive alien plants such as bramble Rubus species are a problem in certain areas, but they are actively controlled.
Impendle Nature Reserve consists of a series of farms that were first settled by colonists more than 100 years ago. Most of the land was devoted to cattle grazing, but small areas have been used for crops. The farms were purchased in the late 1970s by the government for the purpose of consolidating the old KwaZulu homeland and they have been uninhabited since 1980. The value of this Trust Land to conservation was recognised in 1983 with the proposal to formally convert the area into Impendle Nature Reserve. Even though EKZNW has been the management authority for Impendle since 1994, the reserve was only formally proclaimed in 2005.
The reserve holds one of the largest populations of Blue Swallow remaining in South Africa, and its staff monitors this population annually. Research into the breeding biology of the species is also being undertaken on the reserve.