The Functionality Appreciation Scale (FAS; Alleva et al., 2017) is a widely adopted measure to assess appreciation for one's body and its capacity. In this study, we performed a psychometric validation of the Japanese translation of the FAS. Participants included an online sample of 750 Japanese individuals (20–70 years old), who completed the FAS and other previously validated measures of body appreciation, intuitive eating, gratitude, self-esteem, and life satisfaction. Moreover, the survey was conducted twice, 3 weeks apart, to determine test–retest reliability. Exploratory factor analyses replicated the unidimensional factor structure of the FAS, which was also verified by the confirmatory factor analysis. FAS scores had gender invariance, and demonstrated good internal consistency and test-retest reliability over the 3-week period. In addition, further analyzes indicated adequate construct, and incremental validity. These findings indicate that the Japanese version of FAS demonstrates good psychometric properties, and can be used to examine the importance of functionality appreciation for enhancing positive body image and healthy eating.