Due to New Zealand's geographical isolation during its formation, Marlborough like the rest of the country, has virtually no indigenous mammals. One of New Zealand's two native bat species is found in the region in the Pelorus Bridge reserve. Other vertebrates are limited to a variety of bird species, some small reptiles and amphibians, and a variety of freshwater and marine fish. A wide variety of invertebrates are found in the region.
The region is particularly rich in bird life, including a range of migratory birds and species that have introduced themselves from Australia. Many European birds have been introduced and have become naturalised, including some, such as the cirl bunting which has become endangered in its natural habitat in Europe.
A variety of deliberately introduced mammals have become pest species as in other parts of New Zealand, and the same applies to a variety of invertebrates such as various wasp species.