Dyes are one of the ecological problems. In this paper, sea shell as a low- cost adsorbent have been used for adsorption of malachite green, a cationic dye from aqueous solution. In the present study, effects of different parameters, adsorbent dosage (0.05-0.75) g, initial dye concentration (5- 30) mg/l, pH (6-11) and contact time (5- 120) min were investigated. The natural sea shell were characterized by FT-IR analysis. The carboxyl groups on the surface of the sea shell were primarily responsible for the sorption of malachite green dye. The adsorption kinetics was investigated onto pseudo-second-order, Elovich, and intra-particle diffusion models and the adsorption data were best described with the pseudo-second-order model. The paper suggests that the sea shell is a low-cost adsorbent for removal of cationic dyes from aqueous solution.