In this study, the adsorption of methylene blue, a cationic dyestuff, on waste perlite was investigated. Waste perlite is the part of the perlite that remains unexpanded during the expansion process. The effects of pH, amount of adsorbent, contact time, initial concentration and temperature on the adsorption process were investigated. No significant difference was observed in dyestuff removal with the change of solution pH according to the obtained results. For this reason, all experimental studies were performed at the original pH of the solution (pH = 6.80). When the effect of the adsorbent dose was examined, it was determined that the most suitable adsorbent amount was 0.5 g for 50 mL of dyestuff solution at 100 mg/L concentration. In the adsorption experiments with a contact time of 24 h, it was observed that the system reached equilibrium in 7 h. It was observed that the adsorption kinetics of methylene blue on waste perlite fit the pseudo-second-order kinetic model. Maximum adsorption capacity of waste perlite was 9.91 mg/g at 0.5 g adsorbent and 100 mg/L dyestuff concentration for 50 mL solution volume. The adsorption data fit the Langmuir isotherm model. The thermodynamic data (Delta H degrees, Delta S degrees, Delta G degrees) showed that this process is spontaneous and endothermic. At the end of this study, it was seen that the waste perlite is a suitable adsorbent for the removal of methylene blue from wastewater.