The area covered extends roughly from an arc through the villages of Gamblesby, Leadgate and Garrigill southward as far as Milburn in the west and Cow Green Reservoir in the east.

It includes the whole of Cross Fell, the summit of which, at 893 metres asl, is the highest point in the Pennines and in England outside the Lake District.

[3] The area shares many characteristics with the Cairngorms region of Scotland but there are some notable rarities, including a rove beetle, Olophrum assimile, which is known from only one other locality in Britain, a carabid beetle, Nebria nivalis, which has not been found anywhere else in the North Pennines and is known elsewhere in Britain only from North Wales, the Cairngorms and Scafell Pike, and a leiodid beetle, Hydnobius spinipes, which is known from only four other localities in Britain.

Other notable montane and sub-montane species include hair sedge, Carex capillaris, northern bedstraw, Galium boreale, mountain everlasting, Antennaria dioica, and alpine forget-me-not, Myosotis alpestris.

Moorhouse and Cross Fell SSSI was created in 1990 as part of a substantial revision of existing SSSIs that had originally been notified under the National Parks and Access to the Countryside Act 1949.