The adult korora was moulting when it was found by a member of the public.
Once a year, little blues moult to replace any worn out feathers. Over two to three weeks they lose their waterproofing and are unable to swim and hunt for food, so they need to ensure they have enough body fat to last.
The emaciated penguin was taken to The Nest Te Kohanga, Wellington Zoo's native wildlife and animal hospital.
"Through quality food and fluids, we were able to build up the bird's body condition so it was able to complete its moult and be ready for release back to the wild," senior veterinarian Dr. Baukje Lenting said.
"Since being cared for at The Nest Te Kohanga, the korora has completed its moult, regained its waterproofing and is now in a really good condition.
As part of the treatment and care for the korora, it was fed salmon daily and given plenty of time in our salt-water pool to regain feather waterproofing."
Dr Lenting said the zoo was helping to protect little blues, which were considered nationally vulnerable by the Department of Conservation.
"We work together with the Department of Conservation as well as Forest and Bird's Places for Penguins to help protect their species."
Dr Lenting said the community can help in protecting the korora by keeping cats inside at night and keeping dogs on a lead when out and about along the coast.