In this study, carbonized mandarin peel (CMP) was prepared and characterized and the adsorption behavior of the activated carbon for methylene blue (MB) and methyl orange (MO) removal was investigated. Adsorbent (CMP) was characterized by means of scanning electron microscopy (SEM-EDS), X-ray diffraction (XRD), thermo-gravimetric analyses (TGA), and Fourier transform infrared spectroscopy (FTIR). In the adsorption studies, the effects of initial dye concentration, solution pH, adsorbent dosage, and contact time on dye removal were investigated. In the same conditions, MB showed higher adsorption capacity than that of the MO. Therefore, the isotherms, kinetics, and thermo-dynamical adsorption studies were performed for MB. The appropriate adsorption isotherm for MB using CMP was determined as Langmuir isotherm. The kinetic values are well defined by the pseudo-second order kinetic model. The highest MB removal of 99.77% was obtained with CMP concentration of 5 g/L when the dye concentration was 5 mg/L at pH value of 6.9. After solvent regeneration, the adsorbent maintained 95.17% of its regeneration activity. The results show that CMP can be used as a low-cost and natural adsorbent to remove synthetic dye from the effluent of the textile wastewater.