One person in the car died in the crash. No one else has been injured.
Southern Discoveries said in a statement that details were "still coming to light".
"We understand that the driver of the car passed away at the scene and our condolences go out to their family and friends," the company said.
"The driver of our bus as well as all 14 passengers on board are uninjured. We are currently taking all of the passengers back to their accommodation in Queenstown and providing them, as well as our staff, with any support they may require.
"We will cooperate fully with all authorities involved in this incident."
Police said the Serious Crash Unit will investigate and the road would be closed for several hours. There are no diversions available so motorists are asked to avoid the area.
Three fire crews were in attendance, a Fire and Emergency New Zealand spokesman said.
Freelance photographer James Allan, who is on the scene, said the crash was about 10km south from Jack's Point.
It appeared the two vehicles had crashed head-on near a corner, he said.
"The car has gone under the bus and bounced back out in the middle of the road."
There were six police cars and fire trucks on the scene at 8.50am.
"There is a massive pile of taxis coming to pick up the tourists."
The crash comes two days after a person was seriously injured in a head-on collision between two cars on State Highway 6 near Devil's Staircase.
St John communications adviser Chrissy Hamilton said one person was flown to Dunedin Hospital with ''serious injuries'' after that crash and two other patients were transported to Lakes District Hospital by ambulance with minor injuries.