The present study investigated the use of pretreated fish bone (PTFB) as a new surface, natural waste and low-cost adsorbent for the adsorption of Methyl green (MG, as model toxic basic dye) from aqueous solutions. The functional groups and surface morphology of the untreated fish bone (FB) and pretreated fish bone were characterized using Fourier transform infrared (FTIR), scanning electron microscopy (SEM) and Energy dispersive X-ray spectroscopy (EDS),respectively. The effect of operating parameters including contact time, pH, adsorbent dose, temperature, and inorganic salt was evaluated. Langmuir, Freundlich and Temkin adsorption isotherm models were studied and the results showed that the adsorption of basic dye followed Freundlich isotherm. Kinetic modeling of the data at different temperatures confirmed pseudo-second-order(P-2-O) model, along with calculated thermodynamic parameters depicted that the adsorption process is spontaneous and endothermic in nature. Diffusion studies suggested that intra-particle diffusion is not the singular rate- ontrolling factor. The results indicated that 92% of MG capable of being sequestered under optimum adsorption conditions: pH 10.64, adsorbent dose 0.1 g/L, and 60 min contact time. Finally, the results showed that the pretreated fish bone can be effectively used as a proper adsorbent for the adsorption of cationic dye from aqueous solutions.