Nano-twins microstructures were introduced in a high carbon manganese steel by a novel flash thermo-mechanical treatment in order to achieve high resistance to hydrogen embrittlement. Nano-twinned grains decreased hydrogen diffusivity through the bulk material, although it absorbed more hydrogen than the twins-free specimens. Moreover, it was shown that after electrochemical hydrogen charging, the nano-twins microstructures can reduce dislocations glide during plastic deformation, resulting in forming of fine twin plates.