Emergency medical treatment was given, but the man died at the scene, police said.
Police said they attended reports of disorder on Seaforth Rd in Bowentown shortly before 1am.
Police said investigations are ongoing and there are no further details at this stage.
A roadblock was put in place restricting access to the Bowentown peninsula, where Seaforth Rd reaches the Bowentown Beach Holiday Park. It was lifted later in the day.
Waihī food truck owner Roy Steed wasn't able to operate at Bowentown until 10am due to the cordons.
His ice cream truck Taku Moemoe'a was then parked in Anzac Bay serving people next to a newly set up mobile police station.
Steed said: "It's tragic, someone's family member has passed on suddenly."
He praised the way police had handled the situation.
"The communication hub, the mobile station is going to be here for a few hours to try and help the public out."
He said the nearby Bowentown Beach Holiday Park and the wider Waihī area had been very busy during the holiday period so far.
"I know since the 27th Bowentown camp has been full, at capacity, so it could be anyone affected."
Bowentown Beach Holiday Park owner Mike Crosby said staff "were made aware of the incident that occurred outside of the park in the early hours of the morning, New Year's day".
"Our sympathies are with the family and friends of this person and we understand the police have a full investigation under way, which we are assisting with in any means possible."
Waihī Beach Community Board chairman Ross Goudiesaid he heard "emergency serices go down the road in the middle of the night".
