Emergency services were called to the crash near Paparoa, 45km northwest of Wellsford, about 2.15pm.
Senior Sergeant Pat Davis said another person was trapped while two had suffered moderate injuries in the crash on The Pines Rd, off State Highway 12.
The Northland Rescue Helicopter flew to Paparoa Domain to collect the injured patients and take them to Whangarei Hospital.
Police and St John paramedics were at the scene while fire appliances from Maungaturoto were also attending.
One of the vehicles involved was on fire.
Since the beginning of the year 90 people have lost their lives in car crashes, compared with 75 in the the corresponding period last year.
Two teenagers died early yesterday after a high-speed head-on collision at Amberley, north of Christchurch.
All this comes after a horror weekend on New Zealand's roads in which nine people were killed in crashes between March 9 and 11.
Last week, assistant commissioner for road policing, Sandra Venables, called the high number "disappointing".
"Decisions drivers make impact not only them and those in their vehicle, but everybody else on the road as well," she said.
She said police focused on addressing four behaviours they believed were behind a bulk of crashes on our roads; "people driving too fast for the conditions, people driving impaired, people driving distracted and people not wearing seatbelts".
"Nobody wants to share the road with someone who is taking risks."
But an independent road safety consultant is unconvinced lifting the driving age would have a serious impact on the country's road toll.
Road safety consultant Peter Sheppard today told Newstalk ZB's Mike Hosking, adolescents weren't the problem.
"If you have a look at the statistics at the moment, generally there's not a large increase in fatalities in that age group.
"Our increase in our road deaths is happening in higher age groups."
However, it was not just the age which was concerning, but also the training drivers were getting.
"There's always room for improvement in those sorts of areas," he said.
"I think we're starting to get it right, but we've got lots of work we can do."
