In the wild, marmosets cling on to their parents.
Marmite's getting plenty of cuddles from the toy monkey, so hopefully he won't miss his mum too much.
His keepers at Longleat Safari Park in Wiltshire are hoping that Marmite's real mum, Michelle, will grow to like her son.
She rejected him after a particularly painful birth, but she seems to be getting better now.
In the meantime, Marmite's keepers are feeding him using a tiny syringe.
It's a round-the-clock job - Marmite needs to tuck in every two hours!