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The mechanical properties, particularly, yield strength and ductility of metals, exposed under irradiation usually degrade due to generation of primary and secondary defects such as dislocations, vacancies, gas-bubbles, etc . Using atomistic simulations, we have shown that irradiation-induced Helium gas-bubbles are not always detrimental and can contribute to the plastic deformation that leads to improved strength and ductility of the host metal. However, the inter-bubble distance plays a strong role on controlling the mechanisms that operate during elastic and plastic deformation. When the inter-bubble distance is comparatively low (order of 3–4 nm), the copper nanopillar hosting He gas-bubbles exhibits lower yield strength but improved strain hardening rate, and ductility, via coalescence of bubbles that leads to a homogeneous plastic flow. In contrast, higher inter-bubble distance, order of 10 nm, shows a higher yield stress, large stress drop after yielding, and shear localization via shear band formation and bubble fragmentation. Similar inter-bubble distance dependent plasticity mechanisms in He nano-bubbled copper have also been observed in recent in-situ transmission electron microscopy experiments.