Ritchies Coachlines regional manager Malcolm Budd said a Ritchies bus was transporting about 35 cruise ship passengers to Olveston Historic Home when it caught fire in Highgate, Maori Hill.
The electrical fire started in the engine bay at the rear of the bus, he said.
When the driver noticed the fire about 3.30pm, he evacuated the bus and called emergency services.
Roslyn Fire Station station officer Brent Foster said a warning light on the dashboard of the bus alerted the driver to the fire.
The driver unsuccessfully tried to put out the fire with a hand-held fire extinguisher.
When firefighters arrived, dark smoke was billowing from the bus. The crew extinguished the blaze using a reel hose, Mr Foster said.
Another bus was sent to pick up the passengers and continue the tour.
