It happened Saturday afternoon on Highway 2 between Edmonton and Slave Lake.
Police say the injuries were minor, and that people were either treated and released at the scene or brought to hospital.
The bus was on a route operated by the Northern Express Bus Line Company, and it had left Edmonton earlier in the day on its way to High Prairie.
Jean Juckes with Northern Express says the company leased the vehicle for the day from MPM Canada in Edmonton.
Police are still investigating the incident, but say a mechanical problem may be responsible.
They say there were 14 passengers and the driver on board. Six were brought to hospitals in the surrounding area.
Police say most of the injuries are a result of people being bounced around in the bus.