Wellington Free Ambulance will take over ambulance services in Wairarapa from March.
The service will replace the Wairarapa Ambulance Service in what's described as a cost-saving move with benefits for staff and patients.
The National Ambulance Sector Office has been working with the Wairarapa District Health Board since July to select an alternative provider of ambulance services to the region.
Wairarapa DHB chief executive Tracey Adamson said a review had shown ambulance compliance costs were increasing, and the local service was too small to meet additional registration, staff and technology costs.
All existing ambulance staff, including volunteers, would be offered the chance to transfer to the new service, so no jobs would be lost, she said.
"Most importantly, there will be no change to the way people access ambulance services - you can still call 111 in an emergency, but in future there will be no part-charge."
Operations manager for Wairarapa Ambulance Service Glen Worthington said staff were happy with the process and the decision that was made.
"We've had staff involved in the whole process, both from an operational perspective, and also with our two union representatives. It's a relief to have a clear direction for our staff leading into the new year," he said.
"Because so many of our transfers are to Wellington and Hutt Hospitals, it will be good to be part of one organisation that serves the Greater Wellington region. The benefits for staff will be improved training and the ability to keep increasing their skills for the benefit of the people we serve."
Wellington Free Ambulance acting chief executive Andy Long said the service was no stranger to the Wairarapa, having worked with the DHB ambulance staff and the community for a number of years.
"Wellington Free Ambulance has an enviable track record as an innovative and forward thinking service provider."
Ms Adamson said the arrangement would not change St John's Wairarapa role, ranging from training ambulance staff and volunteers to event attendance and youth work.
"I would like to take this opportunity to honour and acknowledge the contribution that St John Ambulance continues to make in the Wairarapa, with their excellent work in first-response assistance in South Wairarapa, training staff, teaching first aid, working with young people, and supporting local events."