Abstract: An inflatable storm window includes flexible and transparent front, back and side walls made from plastic material. Interior spacing support walls made from the same material provide rigidity. The walls are joined together in an airtight manner forming an inflatable box-shaped storm window to fit within a window opening. A valve extends from one of the side walls to admit air or some other gas to inflate the storm window in situ. A compressible seal member is adhered to the side walls about the entire periphery of the storm window for sealing within the window opening.