Objectives: Recently, occupational health specialists (OHS) are expected to exert leadership to develop high-quality occupational health activities. This study aimed to develop and investigate the reliability and validity of a scale to measure leadership preparation among OHS (The University of Tokyo Occupational Mental Health [TOMH] Leadership Checklist; TLC). Methods: Based on literature reviews and interviews among OHS, we created potential items consisting of 54 items with six factors (10 items for self-awareness, 10 items for situational awareness, 9 items for vision, 12 items for mindset, 3 items for performance of one’s duties, and 10 items for relationship-building). An online survey was conducted with 300 OHS in Japan to verify the scale’s reliability and validity. Results: Consequent to the exploratory factor analysis, using the principal factor method and promax rotation, 51 items across the following five factors were identified; “self-awareness”, “situational awareness”, “vision”, “mindset”, and “performance of one’s duties”. The confirmatory factor analysis showed good fit indices; CFI = 0.877, SRMR = 0.050, and RMSEA = 0.072. Cronbach’s α ranged from 0.93–0.96. Additionally, the scores of the TLC were significantly positively correlated with work engagement, job satisfaction, and self-efficacy; contrastingly, they were significantly negatively correlated with psychological distress (p < .05). Furthermore, the participants who had experience leadership without authority indicated significantly higher scores of the TLC and its subscales than those who did not (p < .001). Discussion and Conclusions: The newly developed TLC appeared to have acceptable levels of reliability and validity. It would be beneficial for OHS to show good leadership.