Firefighters were called to a car park on Garswood Street, Ashton, at 11.30pm on Sunday where a silver BMW 3 series had been deliberately set alight.
The flames spread to a black Nissan X-Trail parked next to it.
Crews from Wigan spent two hours tackling the fire, which completely burned out both cars but did not spread to any further vehicles.
Police officers attended to investigate and hoped to examine CCTV footage from the area.
Anyone with information about what happened is asked to call police on 101.