Abstract: In the present work, we applied a novel mass transfer model in the determination of the overall biosorption rate of Methylene Blue (MB) onto natural mexican Agave Kerchovei Lem. fibers. The experiments were performed on an ascending-flow fixed batch adsorber at pH values of 4, 7 and 9 as well as temperatures of 25, 35 and 45 °C using the equilibrium concentration and uptake to describe the isotherm behavior. The textural characterization of the fibers demonstrated a very low surface area (S_BET = 1.06 m²/g) and null porous structure, meanwhile the optical characterization demonstrated a cylindrical geometry with an average particle diameter of 0.02 cm. The biosorption isotherms presented predominantly Langmuir behavior, as well as a combination of electrostatic and π-stacking interactions. The traditional model analysis demonstrated that the PFO model better described the experimental data, however, its constant was affected by operating conditions other than temperature, indicating that this model is not well suited for the description of this biosorption system. In contrast, the Diffusion-Permeation model was able to predict the concentration decay data better, as well as providing physically consistent transport parameters. The increase in the operating conditions accelerated the diffusion-permeation process due to higher electrostatic attraction and solute molecules containing more energy to diffuse and permeate at a higher rate when increasing pH and temperature respectively. The better description of the biosorption phenomena through the biosorption mechanisms, described by the surface chemistry and diffusion-permeation mechanisms allows the design of large-scale biosorption columns that allow greater removal of cationic dyes such as MB from wastewater using an economical and effective biosorbent.