The aim of this study is to reduce the flammability of polypropylene (PP) by adding an organic nano-sized flame retardant into the PP matrix. In order to compare the effects of adding N-containing zirconium organophosphate and graphene oxide (GO) decorated N-containing zirconium organophosphate to PP, PP/zirconium 2-(2-(2-aminoethylamino)ethylamino)ethylphosphonate (PP/Zr(AE)₃P) and PP/GO-decorated zirconium 2-(2-(2-aminoethylamino)ethylamino)ethylphosphonate (PP/GO-Zr(AE)₃P) nanocomposite films were prepared, and their flame resistance evaluated. The structure and morphology of the novel flame retardants were characterized by Fourier transform infrared (FTIR) spectroscopy, and other properties of the nanocomposites were studied by thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), limited oxygen index (LOI), cone calorimeter tests, vertical flame and mechanical tests. The results reveal that both the addition of Zr(AE)₃P and GO-Zr(AE)₃P improve the flame resistance of PP but GO-decorated films exhibited other advantages. Moreover, the evaluation of the thermal properties demonstrated that the addition of Zr(AE)₃P or GO-Zr(AE)₃P to PP improves the stability of PP, and leads to a higher char yield at higher temperatures.