A large bus packed with tourists failed to negotiate a downhill curve and crashed into a wall of rocks at the side of the road.
Local police say 27 people died. Ten are being treated at a hospital for injuries.
The bus was traveling from the Cameron Highlands, a leading summer destination in Malaysia, to the capital city of Kuala Lumpur. Most of the passengers were tourists from neighboring Thailand.
Monday's accident follows other fatal bus accidents in Malaysia this year. In August, 22 people died in an accident attributed to a bus driver dozing off at the wheel. And a man driving without a license caused a bus accident in October that killed 7 people.