A portable, inflatable flood wall is characterized by a sheet of synthetic plastic material which is folded back on itself to define a chamber between bottom, rear and front portions of the sheet and within which at least one inflatable bladder is secured. When the bladder is inflated, the rear portion of the sheet is erected to a vertical position which prevents water from passing beyond the sheet. The front portion preferably contains a plurality of openings to allow water to enter the chamber. The weight of the water on the bottom portion of the sheet serves to hold the wall in place. A plurality of such walls may be connected in end-to-end relation to construct a wall of a desired length.