A new adsorbent, the pistachio nut shell was investigated as an inexpensive and effective adsorbent for adsorption of the commercially important reactive azo dye, Remazol Rot RB (C.I. Reactive Red 198) from its aqueous solution. Taguchi method was applied to determine optimum conditions for the removal of dye from synthetic textile wastewater. After the parameters were determined to remove Remazol Rot RB (C.I. Reactive Red 198) from synthetic textile wastewater, the experimental studies were realized. For this purpose, a series of batch adsorption tests were carried out to address the effect of various experimental parameters and their ranges such as adsorbent concentration, contact time, initial dye concentration, pH, temperature, adsorbent particle size, agitation speed, respectively. An orthogonal array L27 (7(3)) for experimental plan and the smaller the better performance statistics formula were selected to define optimum conditions. The optimum conditions were found to be as follows: contact time (min), 10; agitation speed (rpm), 100; initial dye concentration (mg/L), 25; pH, 2; temperature (degrees C), 20; adsorbent particle size (mm), 0.025 < x < 0.5; adsorbent concentration (mg/L), 100, respectively. Under these optimum conditions, it was determined that the Remazol Rot RB removal efficiency from textile wastewater was 88%. Also, it was thought that pH, adsorbent particle size and initial dye concentration were important parameters for the performance statistics. Langmuir and Freundlich adsorption isotherms were also studied to model the adsorption mechanism data for Remazol Rot RB (C.I. Reactive Red 198).