OBJECTIVES: Moral distress occurs when professionals cannot carry out what they believe to be ethically appropriate actions because of constraints or barriers. We aimed to assess the validity and reliability of the Japanese translation of the Measure of Moral Distress for Healthcare Professionals (MMD-HP). METHODS: We translated the questionnaire into Japanese according to the instructions of EORTC Quality of Life group translation manual. All physicians and nurses who were directly involved in patient care at nine departments of four tertiary hospitals in Japan were invited to a survey to assess the construct validity, reliability and factor structure. Construct validity was assessed with the relation to the intention to leave the clinical position, and internal consistency was assessed with Cronbach's alpha. Confirmatory factor analysis was conducted. RESULTS: 308 responses were eligible for the analysis. The mean total score of MMD-HP (range, 0-432) was 98.2 (SD, 59.9). The score was higher in those who have or had the intention to leave their clinical role due to moral distress than in those who do not or did not have the intention of leaving (mean 113.7 [SD, 61.3] vs. 86.1 [56.6], t-test p < 0.001). The confirmatory factor analysis and Cronbach's alpha confirmed the validity (chi-square, 661.9; CMIN/df, 2.14; GFI, 0.86; CFI, 0.88; CFI/TLI, 1.02; RMSEA, 0.061 [90%CI, 0.055-0.067]) and reliability (0.91 [95%CI, 0.89-0.92]) of the instrument. CONCLUSIONS: The translated Japanese version of the MMD-HP is a reliable and valid instrument to assess moral distress among physicians and nurses.