The adsorption equilibrium, kinetic, and thermodynamic parameters of brilliant green adsorbed by coconut based granular activated carbon were determined from various initial concentrations (300 ~ 500 mg L-1), contact time (1 ~ 12 h), and adsorption temperature (303 ~ 323 K) through batch experiments. The equilibrium adsorption data were analyzed by Langmuir, Freundlich, Temkin, Harkins-Jura, and Elovich isotherm models. The estimated Langmuir dimensionless separation factor (RL = 0.018 ~ 0.040) and Freundlich constant (n-1 = 0.176 ~ 0.206) show that adsorption of brilliant green by activated carbon is an effective treatment process. Adsorption heat constants (B = 12.43 ~ 17.15 J mol-1) estimated by the Temkin equation corresponded to physical adsorption. The isothermal parameter (AHJ) by the Harkins-Jura equation showed that the heterogeneous pore distribution increased with increasing temperature. The maximum adsorption capacity by the Elovich equation was found to be much smaller than the experimental value. The adsorption process was best described by the pseudo second order model, and intraparticle diffusion was a rate limiting step in the adsorption process. The intraparticle diffusion rate constant increased because the dye activity increased with increases in the initial concentration. Also, as the initial concentration increased, the influence of the boundary layer also increased. Negative Gibbs free energy (-10.3 ~ -11.4 kJ mol-1), positive enthalpy change (18.63 kJ mol-1), and activation energy (26.28 kJ mol-1) indicate respectively that the adsorption process is spontaneous, endothermic, and physical adsorption.