An airbag module case for use with a side-impact airbag module including an airbag cushion and inflator assembly, and two mounting projections extending from the airbag cushion and inflator assembly and. The airbag module case includes an assembly cover and two unitary, flexible retainer arms. The assembly cover is sized and shaped to substantially cover the airbag cushion and inflator assembly, and has an open base sized to receive the airbag cushion and inflator assembly. The open base is partly defined by a first side edge and a second side edge of the assembly cover and a first retainer arm extends from the first side edge and a second retainer arm extends from the second side edge. The first retainer arm defines two spaced-apart projection-receiving holes, and the second retainer arm also defines two spaced-apart projection-receiving holes. The opposed retainer arms are sized and shaped to encircle or tightly hug the airbag cushion and inflator assembly with distal ends of the opposed retainer arms overlapping and positioned so that the two mounting projections extending from the airbag cushion and inflator assembly extend through the two projection-receiving holes defined by the first retainer arm and the two projection-receiving holes defined by the second retainer arm to secure the airbag module case to the airbag module.