The first white kiwi to ever hatch in captivity, Manukura, was born at the wildlife centre in May last year, and her brother Mauriora was born in December.
The latest egg hatched in the centre's kiwi nursery on Monday, said centre manager Kathy Houkamau.
"We did know there was the chance of another white kiwi, so of course we weren't surprised, but it is still exciting for us," she said.
"It is rare enough that two brown kiwi carrying the rare recessive white gene mate in the first place, that they would go on to produce three white kiwi is ... well, we're very blessed."
Ms Houkamau said all three chicks have the same father, and it was likely they had the same mother as all eggs were found in the same place.
She said kiwi typically lay two eggs a year, and the other egg which was found in the nest is due to hatch in the next three weeks. There is a probability it would also be white.
Visitors to the centre may be able to see the chick at feeding time over the next few weeks, depending on how much support the chick needed.
She said unfortunately they can't guarantee viewing as it is really up to the chick and how quickly it begins to feed itself.
Ms Houkaumau said each chick would be assessed individually to see if they would be released into the wild.
Local Maori iwi Rangitane o Wairarapa will name the chick over the next few days.
Chief executive and Pukaha board member Jason Kerehi said: "We have always known the reserve at Pukaha Mount Bruce is a very special and spiritual place, this third white kiwi is confirmation of what we have always known."