Vet surgeon Dr Jonathan Bray said Moomoo was extraordinarily lucky.
"The bolt went in just above the eye but was a glancing blow across the cranium so didn't actually impact on brain tissue at all," he said.
"It was really just a matter of opening up the track so we could clean up the contamination so it would heal up okay."
Dr Bray said the cat's nose and eye socket were injured, but otherwise he was "extraordinarily lucky".
"The velocity of the bolt hitting him would have been quite frightening, so he's very brave. He's very well this morning - bright and happy, the wound is doing fine and he's got nothing that is going to cause him any long-term harm."
Ms Ferrari reported the matter to police, who have referred it to SPCA to investigate.
She said the incident made her "sick to the stomach".
"Everyone that's seen him as been completely shocked. The local vet hadn't seen anything like it," she said.
Ms Ferrari put fliers in letterboxes with the picture of the bolt through the cat's head, and has also posted details on facebook.
She said the incident was concerning, regardless of whether the cat was deliberately targeted. "If this was accidental and Moomoo was just in the wrong place at the wrong time, then it could have been my daughter [that was hit]."
Wellington SPCA marketing and fundraising manager Mark Collyns said it was tragic to see an animal in that state of suffering.
"The circumstances are unknown at this moment, we don't know how it came about, we can only speculate that it was deliberately done," he said.
"If somebody is entirely innocent and it was an accident then they need to come forward and explain themselves."
