Firefighters were called to Wimbledon Hill Road just before 7:30 to a double decker electric bus which was alight outside The Alex Pub.
The bus was evacuated and there are no reported injuries, although a 25 meter cordon was put in place.
TfL says it is working with operator, London General, and the bus manufacturer, Switch, to investigate what happened.
London Fire Brigade was called at 7.21am and the incident was over for firefighters at 10.27am.
Three fire engines and around 15 firefighters from Wimbledon, New Malden and Wandsworth fire stations attended the scene.
Tom Cunnington, TfL’s Head of Buses Business Development, said: “Safety is our top priority and we are working with the operator, London General, and the bus manufacturer, Switch, to investigate what happened. The bus was quickly evacuated and there are no reported injuries.”
