In the context of the global outbreak of COVID-19, there is an urgent need to explore the effects of this pandemic on the mental health of adolescents. The present study aims to adapt and validate a Japanese-version Fear of COVID-19 Scale (FCV-19S) with a sample of adolescent students from Japan. To this end, the Japanese-version FCV-19S, Generalized Anxiety Disorder 7-item scale (GAD-7), Patient Health Questionnaire for Adolescents (PHQ-A), and Perceived Vulnerability to Disease Scale (PVDS) were administered to a sample of Japanese adolescents in schools. The results of statistical analyses revealed that the Japanese-version FCV-19S has a bi-factor model consisting of the emotional response factor and the physiological response factor, with a high reliability (emotional: α = .71; physiological: α = .82). Constructive validity was shown by the significant positive correlation between the GAD-7 and emotional (r = .11) and physiological response (r = .25), between PHQ-A and physiological response (r = .19), as well as between both factors and the PVDS subscale (rs > .16). Taken together, these results indicate that the Japanese-version FCV-19S has a high internal consistency and a moderately good construct validity.