It was a Straitsman staff member who was injured on the main vehicle deck of the ferry, a Maritime NZ spokesperson said.
The Maritime Union’s Wellington branch secretary Jim King said the staff member appeared to have suffered an injury to his wrist or arm, as well as bruising down the body.
He is a member of the union, King said.
King has spoken to Bluebridge and said representatives from the company were with the man in hospital.
”Our concern and thoughts are with him and his family.”
King said it was possible the man would be released from hospital today.
They were still working to make contact with him and offer him any support needed to “make sure he’s looked after”.
A hospital spokesman said the patient was in a stable condition in the emergency department.
Maritime NZ earlier told the ship’s Master the vessel must remain at the dock until an investigation has been completed.
By 11am, Maritime NZ said the vessel had been released from the scene but the investigation was ongoing.
Bluebridge told passengers on its website Straitsman sailings were currently delayed by about five hours.
“If you are sailing on Straitsman, you will receive an email and text regarding expected departure and final check-in times.”
The incident is the latest in a string of unfortunate events for the Cook Strait ferry operators.
Bluebridge and Interislander ferries have both been hit with breakdowns and engine problems over the past few weeks. Some of the ferries have broken down partway through journeys across the strait.
Multiple sailings have been cancelled and thousands of passengers left stranded as both ferry operators are booked to capacity until mid to late March.
The displaced passengers have had to fork out hundreds of dollars for flights - some abandoning their cars with plans to fly back in a month to retrieve them - and others have had to find medium-term accommodation until they can squeeze onto another sailing across the strait.
The ferry shortage is exacerbated by one of Bluebridge’s vessels, the Strait Feronia, being in Sydney for mandatory drydocking, and Interislander’s Kaitaki being freight-only while it is audited after a breakdown.
The Aratere also broke down in the strait near the entrance to the Tory Channel a short time later, leaving the boat apparently adrift as wild weather from Cyclone Gabrielle approached.