Safe and effective methods for hydrogen storage are still required to expand its usage as an energy carrier. One approach to contribute to solving this issue is to develop a polymer-based composite. In this study, an acrylonitrile-EPDM(ethylene/propylene/diene)-styrene (AES) composite containing nanostructured LaNi5 was produced by wet ball milling (WM) for hydrogen storage, aiming operation at room temperature. The samples were processed as a cylindrical filament for the analyses performed. Improved particle dispersion was obtained for WM-AES/LaNi5, which correlates with increasing the hydrogen sorption capacity. The polymer was able to maintain the specimen integrity after 20 hydriding cycles, avoiding the LaNi5 pulverization and the reduction of LaNi5 crystallite size. The crystallite size was in the nanoscale, reaching nearly 8 nm for WM-AES/LaNi5. Fewer cycles were required to stabilize the hydrogen capacity for the composites. The samples were exposed to ambient air for up to 17 h, and their absorption kinetics were evaluated. The time required to reach 80% of hydrogen capacity after being exposed for 17 h increased 16.7x and 2.5x for ball-milled LaNi5 and WM-AES/LaNi5, respectively. Therefore, it is shown that the polymer reduces the effects of air exposure on its absorption kinetics. This study shows a promising method to produce a moldable polymer composite for hydrogen storage operational at room temperature. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.