Linear accelerators (LINACs) are used to deliver external beam radiation treatments to cancer patients. They can provide individualised treatments based on a patient's specific needs and are operated by radiation therapists.
Ardern said the new machines offered radiation treatment in more regions than ever before, ensuring improved treatment and fairer access to cancer care in the provinces.
They will provide more precise treatment to patients and would help lead to faster recovery times.
"We know for some lung cancers, newer technology can reduce treatment times from as much as six weeks to as little as three days. It can also mean improved life expectancy when every day is precious," Ardern said today.
"A cancer plan that works has to be comprehensive and must include radiation treatment as well as pharmaceuticals and preventative measures."
Ardern said that one in two people with cancer would benefit from the use of radiation therapy.
"But in New Zealand only one in three are currently accessing these services. That's why we are making the single largest Government capital investment in it."
The $25 million spend over three years comes as part of the $1.7 billion the Government earmarked for health services in May's Budget.
At the moment, if someone living in Northland, Hawke's Bay and Taranaki need treatment, they have to travel to larger cities.
Ardern said today's announcement will mean 1200 people each year will be able to access radiation treatment locally rather than travelling long distances.
The second tranche of the Government's cancer response plan will be the release of the Interim Cancer Action Plan later this month.
Before the 2017 election, Labour promised to put $20 million towards setting up a National Cancer Agency.
Speaking to Breakfast last week, Clark hinted that a plan for such an agency was being developed and would be unveiled soon.
"I'm determined to get the plan right – we won't be rushed into doing that; we want to make sure we get the plan right and that's backed up by action."
New machines will be installed this year at the Auckland, Canterbury, Capital & Coast (Wellington) and MidCentral (Palmerston North) DHBs (two machines).
MidCentral is intending to locate a replacement LINAC in Hawkes Bay in 2020/21 and Taranaki the following year.