New green nanocomposites were prepared based on poly(vinyl alcohol) (PVA) with cellulose nanocrystals (CNC) and functional Fe3O4 (FMNP). Fe3O4 nanoparticles were grafted with maleic anhydride by three step reactions. As a potential adjuvant, FMNP was used in a PVA system with and without CNC in order to investigate thermal properties, combustion behavior and thermo-mechanical analysis. By addition of both FMNP and CNC, the corresponding PVA nanocomposite showed very interesting results in comparison with the neat PVA and the systems only using FMNP and CNC. The char yields in thereto-oxidation and inert atmospheres were showed significant increasing and the peak of heat release rate was decreased about 53%. By the incorporation both FMNP and CNC into PVA Dynamic mechanical analysis revealed that the storage modulus and thermal stability were improved especially at high temperatures. (C) 2016 Elsevier B.V. All rights reserved.