Burglars broke into the Esso filling station, in Patcham, between midnight and 1am yesterday (Tuesday 9 June).
The intruders forced the main door at the garage, which is beside the Mill Road roundabout, before stealing cash and cigarettes.
Sussex Police said that officers were keen to talk to anyone who may have seen any suspicious activity or vehicles in the area during the early hours of yesterday.
Anyone with information is asked to phone Sussex Police on 101, email 101@sussex.pnn.police.uk or call the independent charity Crimestoppers anonymously on 0800 555111.