(class Mammalia)

There are an estimated 18,850 individual specimens representing at least 384 species, with type material for some 263 nominal species and subspecies. The collection consists largely of dried study skins and skulls, with a small selection of skins mounted for display, as well as a few preserved whole or in parts in liquid preservatives.

Collections from various expeditions made between 1900 and 1940 to various parts of Southeast Asia (Malay Peninsula, Sumatra, Java, Borneo, Thailand, Cambodia, Vietnam and various islands on the Sunda Shelf) form the bulk of the collection. These were transferred from the National Museum in the 1970s. They consist mostly of small mammals like squirrels and rats. There is a small collection of larger specimens, particularly primates, donated by a businessman who ran a menagerie in Singapore in the 1930s and 40s. Recent specimens consist of road casualties donated by the public.

Noteworthy are specimens of mammals collected in Singapore in the early 1900s that are believed to be locally extinct there, including the cream-coloured giant squirrel (Ratufa affinis) and the three-striped ground squirrel (Lariscus insignis). There is also the skeleton of a sperm whale (Physeter macrocephalus) found dead in Singapore waters in 2015, which is possibly the largest animal specimen recorded in the country.