Police said the man's car had struck engine problems near McLaren Falls Rd around 4.30am when it was struck by another vehicle.
The Serious Crash Unit is at the scene and motorists are warned to expect delays.
State Highway 29, which was closed for around two hours, had one lane open for traffic travelling in both directions.
Emergency services, including three fire crews, attended the crash.
Fire and Emergency northern shift communications manager Jaron Phillips said no one was trapped in the wreckage but the smash had closed the highway that crosses the Kaimai Ranges for a time.
A witness who drove past the crash scene earlier told Newstalk ZB there seemed to be a body on the road.
The New Zealand Transport Agency said the road was down to one lane with a stop-go sign.
It warned motorists travelling across the ranges to expect major delays in both directions and asked people to delay their journey or use a different route.
Meanwhile, two crashes in West Auckland this morning caused road closures and left two people injured.
Two people were injured after a car rolled on Henderson Valley Road, near Sunnyvale.
A police spokeswoman said the accident happened around 5.26am.
One person inside the vehicle was taken to hospital with serious injuries and a second person suffered moderate injuries.
Auckland Transport said a serious crash has closed a section of the road.
Auckland Transport says motorists are not able to pass either side of the crash between Gum and Mountain Rd and to take a different route.
Two vehicles were involved in a separate crash in Swanson that has blocked off part of the road.
Police and St John ambulance crews rushed to the scene on Swanson Rd shortly after 7am.
No injuries were reported following the crash.
