Aluminum and its alloys are known to be susceptible to hydrogen embrittlement, however, current experimental techniques face significant challenges in directly observing hydrogen atom distributions and their interactions with microstructural features in Al alloys. In this study, we investigate hydrogen-enhanced decohesion at Al/Al₃Li interfaces in Al alloys using a systematic first-principles approach. Our results demonstrate that hydrogen atoms preferentially occupy at strained locations within both Al and Al₃Li phases, with the Al/Al₃Li phase exhibiting a stronger trapping capability at the Al/Al/Al₃Li interface. This hydrogen distribution leads to reduction in cohesive strength of Al/Al₃Li interface. Moreover, we show that the extent of hydrogen-enhanced decohesion on Al/Al₃Li interface is influenced hydrogen concentration and temperature. These findings provide fundamental insight into hydrogen trapping and embrittlement mechanisms at Al/Al₃Li interfaces and offer guidance for designing Al–Li alloys with improved hydrogen resistance through targeted control of composition and microstructure.