<p>Micropillar compression tests were used to investigate the influence of hydrogen on the deformation behavior and hydrogen embrittlement (HE) of nitrogen-alloyed austenitic stainless steel QN2109. Results indicate that the hydrogen increases the dislocation density, reduces the yield stress, and accelerates the formation and intersection of slip bands, with hydrogen-induced cracks initiating at slip band intersections. X-ray diffraction confirms the absence of martensitic transformation, ruling out the role of martensitic transformation in HE. The micropillar compression technique is highly sensitive for characterizing hydrogen-material interactions, owing to the material’s low hydrogen diffusivity and the small size of its hydrogen-affected zone. These findings align with the hydrogen-enhanced localized plasticity mechanism.</p>