As soon as the kittens are passed to Koko, she wraps her arms around them and then starts tickling and playing with the tiny creatures.
Koko can be heard purring as she plays with the kittens, nicknamed Tiger and Blackie, and looks fascinated by her furry friends. She even tries to show one of the kittens how to eat a toy slice of cake, putting it to her mouth and then offering it up to the kitten.
The Gorilla even tries to take one of the kittens back to her room with her, putting it on her back before leaving the room.
Dr. Penny Patterson, who can be heard talking on the video, has worked with Koko for 30 years - teaching her sign language in the process.
The adorable footage has been viewed by half a million users since its posting. Take a look at it below.