Batch adsorption experiments were carried out for the adsorption of cationic dye from aqueous solution onto composite activated carbon. The composite activated carbon was prepared from brewer’s spent grain and sea bean shell at a ratio of 1:1. The equilibrium studies were done at different concentrations and temperatures. The equilibrium data were fitted to Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin isotherm models. The results showed that both Lagmuir and Freundlich isotherm model fitted the data reasonably well but Freundlich isotherm fitted better in the temperature range studied. This confirmed that the adsorption is heterogeneous, non-specific and non-uniform in nature. Kinetic studies were also undertaken in terms of first order, second order, pseudo first order, pseudo second order, Elovich, Boyd, and intra-particle diffusion models. The results indicated that the data followed pseudo second order model with surface adsorption and intra-particle diffusion concurrently operating during the adsorbate- adsorbent interaction. The values of the thermodynamic parameters computed from Van’t Hoff plot confirmed the process to be endothermic and spontaneous in nature