In this work, Hordeum murinum as a sustainable and cost-effective biosorbent material is utilized without any further treatment to remove Methylene blue dye from aqueous solutions. The effects of various parameters including pH, biosorbent amount, reaction time, initial concentration, and temperature are investigated. The results show that 94% of Methylene blue is removed using the optimal adsorption conditions of pH 5.6, biosorbent dose of 0.1 gm, 60 min equilibrium contact time, 20 mg/L of initial dye concentration at a temperature of 25 °C. Experimental results reveal that the adsorption kinetics can have the best description by employing the pseudo-second order model. The spontaneous and exothermic nature of the adsorption process is indicated by the negative values of the Gibbs free energy change and the enthalpy change, respectively. These results reveal that Hordeum murinum exhibited excellent performance for the removal of Methylene blue from aqueous solutions, which can make it very interesting as an alternative and effective low-cost biosorbent material.