Graphical Abstract: The feasibility of using Retama raetam, for the cationic dye (methylene blue) adsorption from simulated aqueous solution, has been investigated as a low cost and an eco-friendly adsorbent. The methylene blue maximum adsorption occurred at pH 8 and the lowest adsorption occurred at pH 2. The apparent equilibrium was reached after 120 min. Adsorption modelling parameters for Freundlich and Langmuir isotherms were determined and, based on R2, various error distribution functions.