["Japanese Psychological Research, EarlyView. ", "\nAbstract\nThis study developed and validated a Japanese version of the Human Capital Sustainability Leadership Scale (HCSLS‐J), a measure designed to assess the leadership that fosters the sustainable growth of human capital. A sample of 527 Japanese supervisors (500 male, 27 female) completed the HCSLS‐J along with measures of leadership, civility, well‐being, mental health, and stress mindset. Confirmatory factor analysis supported the original four‐factor structure (ethical, sustainable, mindful, and servant leadership), which demonstrated high internal consistency. The HCSLS‐J showed strong concurrent validity, correlating positively with effective leadership behaviors, workplace civility, well‐being, and mental health. Notably, higher HCSL Scale scores were associated with viewing stress as debilitating, suggesting leaders high in HCSL may be more attuned to follower distress. While the HCSLS‐J proves to be a relevant and valid tool for the Japanese context, high inter‐factor correlations and reliance on self‐report data highlight the need for future research on its discriminant validity using multisource methods. This study provides both a foundational tool and a clear agenda for advancing HCSL research in Japan.\n"]