[4] Muir of Dinnet was first declared a NNR in 1977 due to its value as a habitat for flora and fauna, and its important geomorphological features,[5] the most striking of which is the Burn O'Vat.

[8] Most of the area is underlain by pink-coloured granite, which formed around 425 million years ago by the slow cooling of rocks that had been melted by heat during the formation of a large chain of mountains.

The area around and to the south of Loch Kinord consists of an older group of rocks, known as the Dalradian series, that were laid down as layers of sand and mud on the floor of an ancient ocean around 600 million years ago.

The climate warmed rapidly at the end of the last ice age, following which huge quantities of water were released, washing silts, sands, gravels and rocks across the landscape, leading to the formation of many discernible glacial features across the Muir of Dinnet, including kettle hole lochs, kames and eskers.

One of the most impressive features at the Muir of Dinnet is the gorge and giant pothole known as the Burn O'Vat (or simply 'the Vat'), which was carved when a meltwater river encountered an area of hard bedrock, leading to the formation of a whirlpool.

The lochs of the reserve are of international importance for wintering wildfowl including whooper swans, goldeneye, wigeon, teal, mallard and tufted duck.

[15] Otters are also regularly seen at Muir of Dinnet NNR, along with seven other UKBAP mammal species, such as red squirrels and pipistrelle, Daubenton's and brown long-eared bats.

In 1949 the Muir of Dinnet was identified as a potential national nature reserve by the Scottish Wildlife Conservation Committee, however this was not acted upon at the time.