The first part of this investigation focused on the synthesis and characterization of a hyperbranched intumescent flame-retardant (HIFR) agent. Two steps were used in the synthetic process. The structure was characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). The second part focused on the application of HIFR agent into natural rubber (NR) composites. The cure characteristics, tensile properties, wear resistance, and flame-retardant property of HIFR/NR composites were evaluated. It was demonstrated that the addition of this HIFR agent into NR led to an improvement in its physicomechanical and flame-retardant properties. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 3474-3482, 2011