Emergency services received reports of a two-vehicle crash, near Lake Rotomā, at 10:15pm on Thursday night.
Hato Hone St John says a dozen patients were "assessed and treated on the scene."
It says 12 patients were taken to hospitals across the region.
One patient with critical injuries was flown to Waikato Hospital, while a second patient was flown to Tauranga Hospital, in serious condition.
Nine people sustained moderate injuries: two were transported to Whakatāne Hospital, and seven taken to Rotorua Hospital.
One person with minor injuries was taken to Rotorua Hospital.
St John says one rapid response unit, six road ambulances, two helicopters, two road managers, and one major incident support unit were at the scene.
MetService Has Issued a Heat Alert for Whakatāne Today
Road Works Ramp up on State Highway 2
Severe Thunderstorm Watch in Place For The Bay of Plenty
Athletes, Amputees, and Disabled People Are Encouraged to Compete in Born to Adapt, in Rotorua's Redwood Forest
