The bullet entered and left the kitten's right shoulder, leaving it with a "serious" large exit wound.
It ran and hid inside its family's caravan before being taken to a veterinary clinic in Oamaru, where it was tended to.
Palmer told the police he thought the kitten was feral and that he believed he had the right to shoot.
The court heard the camp site didnot permit guns onsite.He had apologised to the kitten's owner, was remorseful and paid Oscar's veterinary bill of $1413.99.
Judge Joanna Maze said it could be a very powerful thing for a 12-year-old child to see a mature man apologise.
Palmer was convicted and discharged.