Experimental and numerical investigations are performed to evaluate the mass diffusion in Agave Americana natural fiber composites considering several environmental conditions. The effect of fiber pretreatment by alkaline hornification is analyzed on the moisture uptake behavior of the Agave fiber composites. It was observed that water retention value, which is a measure of affinity towards moisture, reduces with each subsequent hornification cycle. The microstructural investigations were performed to analyze the morphological changes in fiber microfibrils. Composite specimens were subjected to accelerated ageing under water and humidity conditions at controlled temperatures between 0 degrees C and 75 degrees C. Composites were weighted periodically and mass gain curves were analyzed. A comparison is drawn between the mass gain behavior of composites fabricated using untreated and alkali hornified Agave fibers. The studies have revealed a clear influence of alkaline hornification on the improvement of the hydrothermal durability of the Agave fibers. The effective moisture diffusivity of the composites is determined using edge correction factors for rectanguloid specimens. Finally, the experimental mass gain is compared with the numerical Fick's law based finite element (FE) approximations. (C) 2018 Elsevier Ltd. All rights reserved.