A police spokeswoman said the crash, which happened on State Highway 1, occurred about 8.35am.
The SUV had rolled onto its roof and the truck and trailer has ended up off the road in a ditch near the railway line.
Debris from the crash is on both the road and the railway tracks.
The crash happened near the Taieri River Bridge and the turnoff to Henley.
One person was trapped and needed to be freed, the police spokeswoman said.
"The driver of the car is injured".
A St John spokeswoman confirmed one person was taken to Dunedin Hospital in a critical condition.
One ambulance and one rapid response unit responded to the scene, she said.
The Southern District Health Board said the patient was in a stable condition.
The Serious Crash Unit was in attendance earlier.
The road was closed for most of the day and fully reopened just before 5pm.
