Polyurethane foam found in household furnishings and bedding creates a severe fire hazard, resulting in loss of life and property each year. In an effort to reduce the flammability of polyurethane foam, a polyelectrolyte multilayer (PEM) coating, comprised of polyethylenimine and polyacrylic acid-stabilized aluminum hydroxide (ATH), was deposited onto foam using layer-by-layer (LbL) assembly. PEM coatings with and without incorporation of ATH were deposited and compared to assess the effectiveness of ATH on flame suppression. All recipes resulted in conformal coatings, maintaining the open cellular structure of the foam. Only three bilayers of PEI/PAA-ATH retained the shape of foam after exposure to a butane torch flame for 10 s. With six bilayers, the flame was extinguished, which prevented flashover. Cone calorimetry revealed that this 6 BL coated foam exhibited a 64 % reduction in peak heat release rate and a 44 % reduction in maximum average rate of heat emission. This work demonstrates an extraordinarily effective flame-retardant nanocoating that uses environmentally benign chemistry and relatively few deposition steps, prepared using LbL assembly.