Textile wastewater has become one of the serious environmental problems due to containing a high concentration of chemicals with extreme color intensity. Reactive red RB is among the synthetic azo dyes commonly used as a textile colorant with their property are very difficult to degrade naturally. This research was focused on studying the kinetic behavior, and adsorption isotherm of reactive red RB textile dye on coconut leaf stalk activated carbon (CLSC). Coconut leaf stalk carbon was activated using sulphuric acid and sodium hydroxide. It was investigated in terms of chemical functional groups, surface morphology, carbon content, ash content, and adsorption efficiency of reactive red RB textile dye under various conditions of initial pH, incubation time, and dye concentration. The results showed the maximum adsorption efficiency of reactive red RB dye with a concentration dye of 60 mg/l onto CLSC surface activated by sulfuric acid and sodium hydroxide in an experiment carried out at pH 5 for 120 min were 88.73% and 64.27%, respectively. The adsorption isotherm of reactive red RB on the CLSC surface follows the Langmuir isotherm model, which shows that the adsorption process occurs monolayer. In contrast, the adsorption kinetics correspond to pseudo-second-order.