A police spokeswoman said the incident happened in Riselaw Rd, near Columba Ave, about 3pm.
It was not yet known why the car went out of control and down a bank into a hedge, she said.
Of the four people in the vehicle one had serious injuries, another had minor injuries and the other two were not hurt, the police spokeswoman said.
The seriously injured passenger was taken to Dunedin Hospital.
Riselaw Rd was closed for a short time while police investigated the incident and the wreckage was removed.