“Fat talk” refers to girlsʼ tendencies to disparage their own and othersʼ bodies in conversations with their friends, which is considered to be related to body dissatisfaction. Although fat talk has been seemingly observed among young Japanese women, its effects on their body image have not yet been studied. The present study aimed to develop a Japanese version of Arroyo and Harwoodʼs Fat Talk Scale and to examine its validity and reliability. The Fat Talk Scale was translated into Japanese and administered to 760 high school and undergraduate students. A principal axis factoring analysis of Fat Talk items yielded the following three factors: “body shape dissatisfaction,” “fear of fat,” and “comparison with others.” Cronbachʼs alphas indicated adequate internal consistency. Three subscales were significantly correlated with body dissatisfaction, sociocultural attitudes toward appearance, and body esteem, indicating good convergent validity. Additionally, 214 high school girls scored significantly higher on the Fat Talk Scale than did 258 high school boys, indicating good known groups validity. The present results confirmed that the psychometric properties of the Japanese version of the Fat Talk Scale were adequate.