In this study, the adsorption kinetics of naphthalene onto organically modified-sepiolite was investigated by means of the effects of pH, contact time, adsorbent dosage and temperature. The modification of natural sepiolite was accomplished with a cationic surfactant, which is namely dodecyltrimethyl ammonium (DTMA) bromide. The surface characterization both natural- and modified-sepiolite were carried out by using FTIR method to observe the intercalation of DTMA between the sepiolite layers. The elemental and thermal analyses were also performed to understand the modification. The optimum pH values and the equilibrium contact time for the adsorption of naphthalene onto DTMA-sepiolite were found as 6 and 75 min, respectively. The kinetic parameters of the adsorption process were calculated from experimental data. According to these parameters, adsorption process follows the pseudo-second-order kinetic model with the high correlation coefficients (r(2) = 0.999). The obtained results show that modified-sepiolite is reasonably effective adsorbent for the removal of organic contaminants, which are an important source for the environmental pollutants.