The tallest land mammal has been entered in the organisation's Red List as a "vulnerable" species, IUCN announced at a UN biodiversity conference in Cancun, Mexico.
These animals are threatened by illegal hunting, civil unrest, mine sand expanding farms, according to the non-governmental organisation that is based in Switzerland.
Less than 98,000 giraffes remain in Africa.
Many bird species also entered the updated Red List, and the African grey parrot was elevated from "vulnerable" to "endangered," which means that it faces a very high extinction risk.
Grey parrots are prized pets because they are able to mimic human speech.
Their numbers are dwindling as too many birds are being trapped and their natural habitat in Central Africa is shrinking.
In addition, wild varieties of food crops such as barley, oats, sunflowers and mango were included on the list.
These wild plants are important because they can be used to breed stronger and more nutritional new crops, IUCN said.
Governments "have the immense responsibility to step up their efforts to protect our planet's biodiversity - not just for its own sake but for human imperatives such as food security and sustainable development," IUCN chief Inger Andersen said.