It is a rare event, the first confirmed sighting of an Emperor penguin in New Zealand in 44 years.
"I saw this glistening white thing standing up and I thought I was seeing things," said Christine Wilton, who found it while walking her dog.
The department of conservation is baffled by how it arrived, saying it may have taken a wrong turn.
"It's amazing to see one of these penguins on the Kapiti coast," says the department's Peter Simpson.
The visitor has attracted crowds of onlookers, who are being advised not to disturb the penguin and keep their dogs on leads.
Conservation experts say the bird is a juvenile, about 10 months old and 32in (80cm) tall.
Emperor penguins are the tallest and largest of all penguin species, growing up to 4ft (122cm) high and weighing more than 75lb (34kg).
Colin Miskelly, a penguin expert at Te Papa, New Zealand's national museum, said the bird was likely born during the last Antarctic winter.
It may have been searching for squid and krill when it took a wrong turn and arrived on New Zealand's North Island.
"Usually they stay among the pack ice," said Mr Miskelly.
"This one just kept going north and it's a very long way from its usual range." (read more)