The crash happened at about 10.30pm on Les Petites Capelles near Guernsey Candles.
Police, firefighters and ambulance staff were all called to the scene.
PC 123 Aaron Cusack said they believed the silver Vauxhall Astra was travelling from the direction of the Pony Inn, but it was unclear at this stage what speed it was travelling. The car is then believed to have hit two walls before going onto its side.
Police suspect that two males were inside the vehicle, as well as a person who was trapped in the vehicle.
The person who was trapped had to be cut out of the vehicle by the firefighters and was then taken to hospital.
One person has been arrested.
Guernsey Police would like to speak to anyone who may have information or a description of the driver or passenger of the vehicle or anyone that witnessed the collision.
Anyone with information should call 72511 and quote crime reference number OC2000008239 or anonymously contact Crimestoppers on 0800 555 111.