Response surface methodology was utilized to optimize the impact strength of polyamide 6 based nanocomposites using three different types of tougheners (ethylene-methyl acrylate, ethylene-ethyl acrylate-maleic anhydride, and hydrogenated butadiene acrylonitrile rubber) at three different levels of clay and rubber. Melt mixing method using a lab scale twin screw extruder was applied to prepare the samples. The wide-angle X-ray diffraction, transmission electron microscopy, and atomic force microscopy results indicated intercalated/exfoliated morphology for all of the prepared nanocomposites. The tensile properties as well as the Izod impact strength of the designed samples were evaluated. Impact resistance was correlated to material variables by using a second order polynomial function. The best balanced mechanical properties, between 15 designed experiments, was achieved using ethylene-ethyl acrylate-maleic anhydride as toughener, 4 wt % of clay and 17.5 wt % of the toughener, whereas 900% improvement in impact strength and 15% enhancement of Young's modulus was obtained compared with pristine polyamide 6 resin. The formulation meeting the simultaneous optimization of Young's modulus and impact strength was proposed based on mathematical quadratic modeling. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 969-979, 2010