The reserve comprises a narrow strip of land that is 3.5 km long and less than 500 m across at its widest point:[3] the total area is 92 hectares (230 acres),[2] most of which is only a few metres above sea level and bounded by cliffs to the west.

[5] The cliffs and dunes provide a nationally important habitat for flowering plants and insects, many of which are at their northern limit in Britain.

[6] A visitor centre run by NatureScot is located within an old lifeboat station, which also provides educational facilities for groups of school children, bird watchers and botanists.

[4] St Cyrus has a warmer climate than much of northeast Scotland due to the warming influence of the sea,[3] and as a result many of the plants found here are living at their northern limits.

Examples of this include species such as maiden pink, wild liquorice, yellow vetch and the carnivorous Nottingham catchfly.

Furthermore, the prevalence of gorse shrub provides a nesting place for such small perching birds as whitethroat, stonechat and yellowhammer.

St Cyrus was formerly renowned for its breeding colony of little and arctic terns: these species have been largely absent in recent years.

[11] There are no archaeological remains on the NNR itself, however the reserve almost completely surrounds the old graveyard known as the Nether Kirkyard, which is associated with former church of Ecclesgreig.