The woman was in one of two vehicles that collided about 25km south of Frankton about 1.30pm.
Senior Constable Terry Erceg, of Queenstown, said a man and a young boy in the same vehicle sustained minor injuries, but two men in the other vehicle had moderate injuries.
They had to be cut from their vehicle, a seven-seater station wagon, by volunteer firefighters.
St John South Island communications adviser Ian Henderson said all five were taken by ambulance to Frankton's Lakes District Hospital for treatment.
The road was closed for more than an hour, causing traffic to back up for about 1km in both directions before one lane was reopened to traffic about 2.40pm.
Snr Const Erceg said the two injured men in one vehicle were New Zealanders, while the three occupants of the other vehicle were overseas tourists.
