A fuel cap barrier kit is basically provided with a movable barrier and an attachment member. The movable barrier is dimensioned and structured to be attached to a vehicle body at a location in which the movable barrier is disposed in front of a fuel cap and is underneath a filler compartment door. The movable barrier is movable between an inlet accessible position in which the movable barrier permits user access to the fuel cap and an inlet blocking position in which the movable barrier is disposed in front of the fuel cap. The attachment member is configured to fixedly attach the movable barrier to the vehicle body.