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This work elucidated the influence of Nb/Mo on the hydrogen embrittlement (HE) resistance of medium Mn steels (MMS) through an electrochemical cathodic charging method, slow rate tensile tests and microstructure characterization. According to the experimental results, the influences of Nb/Mo on HE resistance could be described as follows: (1) Nb/Mo addition could decrease the mean grain size of MMS up to 0.24 lm, which would decrease the hydrogen content per unit area by supporting more grain boundaries;(2) Nb/Mo addition could produce lots of precipitates, which could act as potential stable hydrogen trapping sites; (3) Nb/Mo addition decreased the diffusible hydrogen contents from 3.6 to 2.2 ppm and effective hydrogen diffusion coefficient from 5.6310 -10 to 2.9310 -10 m 2 /s;(4) Nb/Mo addition could increase austenite stability, and decrease transformed austenite fraction. Compared with single Nb addition, multiple Nb-Mo addition could further decrease the mean grain size and precipitate size, increase precipitate density and enhance grain boundary cohesion. Therefore, the Nb-Mo bearing MMS has a good HE resistance.