This research investigates the adsorption of methylene blue dye. Methylene blue is a common cationic dye used in various industries, and its presence in wastewater poses significant environmental and health concerns. Traditional methods for dye removal can be expensive and generate secondary pollutants. Mango leaf powder proves to be a cost-effective and environmentally friendly adsorbent for the removal of methylene blue (MB) dye from aqueous solutions. Characterization was performed through Scanning Electron Microscopy (SEM) for the morphology of the mango leaf powder; Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction (XRD) for the crystallinity of the mango leaf powder; and Thermogravimetric Analysis (TGA) for the thermal stability of the mango leaf powder. Batch adsorption experiments were conducted to evaluate the efficiency of mango leaf powder in removing methylene blue from aqueous solutions. The study employed both Langmuir and Freundlich isotherms to analyze the adsorption data, revealing a higher correlation coefficient for the Freundlich model (R² = 0.932) compared to the Langmuir model (R² = 0.8864). Kinetic studies indicated that the pseudo-second-order model provided a better fit for the adsorption process (R² = 0.8288). Thermodynamic parameters were calculated, showing a Gibbs free energy change (ΔG) of -0.364 × 10⁻³ kJ/mol, an enthalpy change (ΔH) of -0.521 × 10⁻³ kJ/mol, and an entropy change (ΔS) of 2.233 J/mol·K, indicating that the adsorption process is spontaneous and exothermic in nature. Furthermore, a reusability study demonstrated that mango leaf powder can be effectively reused across three cycles without significant loss in adsorption capacity, affirming its potential as a sustainable biosorbent for wastewater treatment applications.