A finishing process with polyhedral oligomeric silsesquioxane (POSS) and bohemite nanoparticles has been exploited for enhancing the thermal stability and flame retardancy of cotton fabrics. The thermal behavior of flame retardant treated cellulosic fabric has been studied by thermogravimetric analyses (TGAs). It has been found that such nanoparticles favor the carbonization of the cellulose and slow down the kinetics of thermo-oxidation in air. At the same time, the finished fabrics have turned out to be more efficient with respect to neat cotton as far as the flame retardancy is concerned, pointing out an increase of the time to ignition (TTI) and a decrease of the heat release rate (HRR). Furthermore, a comparison between the fire performances of the nanoparticles under study and a commercial phosphorus-based flame retardant has been investigated. The morphology and elemental composition present in the treated fabrics have been also investigated using scanning electron microscopy (SEM) coupled to the energy dispersive spectroscopy (EDS), and the results have been compared with the untreated fabric. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 426-436, 2012