This study investigated the adsorption of Malachite Green (MG), a toxic cationic dye, onto natural soda feldspar as a low-cost mineral adsorbent. The effects of contact time, solution pH, initial dye concentration, adsorbent dosage, and temperature were evaluated to optimize the adsorption process. Maximum dye removal was achieved at pH 8, a contact time of 90 min, an adsorbent dosage of 15 g L⁻¹, and higher temperatures. Kinetic studies revealed that the adsorption process follows the pseudo-second-order model, indicating strong interactions between MG molecules and the active sites of soda feldspar. Equilibrium data were best described by the Redlich–Peterson and Langmuir isotherm models, suggesting a combination of homogeneous and heterogeneous adsorption with a maximum adsorption capacity of 34.49 mg g⁻¹. Thermodynamic parameters confirmed that the adsorption process is spontaneous and endothermic. Thus, the results demonstrate that soda feldspar is an effective and economical adsorbent for the removal of Malachite Green from aqueous media, offering a promising option for sustainable wastewater treatment.