The invention relates to a fastening device (16) for a preferably tubular inflator (14) on a vehicle part (18), including a holder component (20) to which the inflator (14) can be fastened. The holder component (20) includes a first fastening element (22) and a second fastening element (24) offset in the axial direction (A) for fastening on the vehicle part (18). The holder component (20) includes a lever support (30) adapted to be in contact with the vehicle part (18) and being arranged in the axial direction (A) between the first and second fastening elements (22, 24) and separating the holder component (20) into a first lever arm (32) and a second lever arm (34). The invention further includes a fastening assembly (38) including an inflator (14) and a fastening device (16), the first fastening element (22) includes a hook (26) formed by a nut (50) screwed onto a threaded bolt (48) of the inflator (14) having a head portion (52) and a tapered neck portion (54) allowing a positive connection to the vehicle part (18).