["Japanese Psychological Research, EarlyView. ", "\nAbstract\nThis study examined the validity of the Japanese‐translated version of the single‐item subjective level of stress (SLS‐1), encompassing three studies. Study 1 tested the understandability of the item wording in a general population (N = 120), which indicated that the wording of the Japanese‐translated version of SLS‐1 is generally understandable. Study 2 tested the face validity of the SLS‐1 among experts and non‐experts (N = 20). The face validity indices supported its relevance to subjective stress and its importance, but not its essentiality. Study 3 tested the convergent validity and test–retest reliability of the SLS‐1 in another general population sample (N = 524). The SLS‐1 showed a moderate positive relationship with the 14‐item Perceived Stress Scale, but failed to meet the pre‐registered criteria. The SLS‐1 showed the expected relationship with stress symptoms and well‐being, supporting its convergent validity, and showed good test–retest reliability. Although some indices did not meet the pre‐registered criteria, the SLS‐1 confirmed face and convergent validity as a measure of subjective stress.\n"]