In this work, poly(methyl methacrylate) (PMMA)/ammonia borane (AB) nanofiber composites were fabricated and the synergetic nanoconfinement effect of nanofibers on dehydrogenation temperature and the removal of unwanted by-products of AB (NH3BH3) were studied. The results of the dehydrogenation of PMMA/AB samples showed an exothermic reaction temperature of 112 degrees C, which is significantly lower than that of pure AB (120 degrees C). Furthermore, the interaction between AB molecules and PMMA nanofiber structures decreased the enthalpy of exothermic decomposition, from -21.00 to -10.66 kJ/mol H-2, suggesting that this type of AB nanofiber composite can provide a convenient reversible hydrogen storage material. Based on the thermogravimetric analysis curves, the use of PMMA to support AB in composite structures resulted in a decrease in AB weight loss from 60.00 to 11.10 wt.% which, in turn, could vigorously reduce the emission of by-product impurities. Based on the obtained results, the strategy of supporting AB in nanofiber structures can be presented as a practical solution to maintain lower operational temperatures and to reduce undesirable volatile products in the dehydrogenation process of AB.