In order to realize a more effective and environmentally friendly flame-retardant treatment for melamine foam, which is expected to be used as highly flame-retardant cellular polymeric materials for building and construction, a novel intumescent flame-retardant nanocoating, comprised of positively charged chitosan (CH) and negatively charged ammonium polyphosphate (APP), is deposited on high open-cell ratio melamine foam using layer-by-layer assembly. SEM images indicate that the bilayer CH-APP nanocoating is deposited on the surface of melamine foam successfully. The LOI value of foam coated with two-bilayer CH-APP is 47.0%, while that of pure melamine foam is 34.5%. Cone calorimetry shows the foam coated with two bilayers of CH-APP to possess excellent self-extinguishing property, and remarkably prevents the foam from shrinking, as a result of the expanded carbonized layer. The peak heat release rate and the total heat release of foam coated with two bilayers of CH-APP are decreased by 87% and 77%, respectively, with only 1.6 wt% of phosphorus incorporation. This CH-APP nanocoating deposited on melamine foam is unique because it needs only two bilayers to be applied, is composed of water-borne, environmentally-benign components, and can prevent ignition and shrinkage of melamine foam. (C) 2015 Elsevier Ltd. All rights reserved.