It is unclear how the eel managed to be trapped inside the man. It is believed medics successfully removed it and the man was later discharged.
A hospital spokesman last night confirmed the bizarre incident had taken place.
"In response to a direct query from the Herald on Sunday, we can confirm that an adult male presented at Auckland City Hospital this week with an eel inside him," Matt Rogers, spokesman for Auckland District Health Board, said.
He added: "No further comment will be made out of respect for the patient's right to privacy."
According to the Department of Conservation website, there are two main types of eel found in New Zealand - the shortfin and the longfin.
Eels migrate up streams as elvers to find suitable adult habitat. After many years they migrate to the Pacific Ocean to breed and die. Eels are secretive, nocturnal and prefer habitats with plenty of cover. They hunt by smell rather than sight.