To investigate the mechanism of hydrogen embrittlement in amorphous membranes, changes in the stress-strain curves of an amorphous Ni90Al10 model membrane as a function of hydrogen concentration were examined using Molecular Dynamics (MD) simulations. In addition, the fractional change of short-range ordered (SRO) structures during uniaxial tensile deformation was scrutinized using the Voronoi tessellation method. By correlating these structural evolutions related to volume expansion with changes in the mechanical property, the hydrogen embrittlement phenomenon occurring in the amorphous membrane was discussed with respect to the abrupt increase in the degree of strain localization during deformation. The possibility, not only of hydrogen embrittlement, but also of hydrogen-induced ductility enhancement, was demonstrated by the decrease in the degree of strain localization. Finally, we proposed a fundamental mechanism that can explain these overall phenomena occurring in the amorphous membrane by the introduction of hydrogen. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.