A large tent was set on fire in a front garden.
Residents at a house in Mitford Walk, Bewbush, awoke at around 3am on Monday (January 28) to find that their trailer tent had been set alight.
Crawley Fire and Rescue Service attended and extinguished the blaze.
Police, who have carried out house to house enquiries and a forensic investigation, said it was an arson attack.
Anyone with information can call police on 101 and quote crime reference number 0091 of 28/01.