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Highlights • Failure location in hydrogen embrittled stainless steel joint depends on pre-strain. • Severe strain-induced α′ martensite in the base metal contributes to failure mechanism transition. • Tendency of strain-induced α′ martensitic transformation for the weld metal and base metal is strongly determined by local chemical homogeneity. Abstract The effects of pre-strain on hydrogen embrittlement of 304L K-TIG welded joint were investigated. As pre-strain of joint increased, fracture location of hydrogen-charged joint changed from weld metal to base metal. In low prestrained joints, fracture may be initiated at the sites of clustered dislocations due to hydrogen in weld metal with a high density of pre-existing dislocations. In high prestrained joints, some regions in base metal suffered severe strain-induced α′ martensitic transformation due to Ni depletion bands and cracking occurred at phase boundaries where may provide more sites for the accumulation of hydrogen atoms and dislocations. [ABSTRACT FROM AUTHOR]