WorkSafe has been notified of a fatality at Ranana, north of Whanganui.
Emergency services were called to the incident on the Whanganui River Rd around 9.25am.
A police spokeswoman said St John had reached the scene via helicopter and the Serious Crash Unit had been dispatched.
A WorkSafe spokeswoman said they understood a tractor was involved.
She said WorkSafe was making inquiries to establish what its next steps might be, including whether or not it would launch an investigation.
Police said no details about the victim would be released until next of kin were notified.