The little boy or girl, who measures no more than 15 centimetres, was born recently to mother Linoa, and is the latest addition to the zoo's family of sifakas.
The animals are a type of lemur native to Madagascar that feed mainly on leaves and nuts.
However, due to deforestation and people hunting them for food, their numbers in the wild are critically low.
There are now only 18 sifakas in zoos across the world, and with infant mortality rates at 80%, the keepers at Belfast Zoo have developed a special training routine allowing them to check Linoa's babies without causing any stress.
Keeper Linda Frew said: "We're pleased to announce the arrival of a very special baby at Belfast Zoo, the latest addition to our sifaka family.
"Five weeks ago, on 19 January, we had our latest addition - a baby, but we don't know what sex it is yet. We have not named it yet though I've a feeling it's a boy."
Belfast Zoo currently has five crowned sifakas and with only two breeding pairs in Europe they play a vital role in the conservation of the species.
Clutching to the arms of its mum, the new arrival looks to be in safe hands.