Abstract: The quest to find hydrogen embrittlement resistant steels to use in hydrogen related energy infrastructures is increasing. So, with this study the effect of hydrogen embrittlement on the mechanical response of high manganese austenitic steel Fe-33Mn-1.1C is investigated. Prior to tensile tests the specimens were electrochemically hydrogen charged, and then tested at different strain rates of 10-2, 10-3, 10-4, 10-5. Macro deformation investigations after fracture showed that hydrogen charging increased yield strength, and furthermore yield strength is increased with decreasing strain rate. Hydrogen charging had a detrimental effect on work hardening ability of high manganese austenitic steel, which is more remarkable in lower strain rates relatively. Microstructural investigations gave us clues about increased yield strength is a result of solution hardening stem from hydrogen charging. Effect of strain rate on increased yield strength with decreased strain rate is suspected to conclusion of hydrogen segregation to the dislocation and increased time for interaction of hydrogen and dislocations. Decreased work hardening rate with decreasing strain rate is a result of decreasing cross sectional area at the equivalent strains. Fractographs showed that with the decreasing strain rate, the brittle fracture area fraction is increasing, and this correlates with the comments above. Both intergranular and transgranular fracture modes observed after fracture surface observation. Further microstructural investigations revealed that crack initiation and propagation stems from plasticity-dominated deformation mechanisms, which is not usual with high manganese steels. High manganese steels usually have trend to plastically deform after deformation twinning and decohesion activities, however, electron-channeling contrast imaging and electron back-scattering imaging results proved this was not the case. Many slip traces observed on fracture surface with the help of scanning electron microscopy images. When this observation combined with the knowledge of high carbon concentration results with the strengthened dynamic strain aging and ease of cross slip; accordingly, both these effects can cause strain localization; it is possible to comment on these above two slip traces, and high stacking fault energy stem from carbon concentration lead to hydrogen embrittlement associated with hydrogen enhanced localized plasticity (HELP) mechanism.