Objective: This study examined the psychometric properties of the parent and teacher forms of the Japanese version of the Strengths and Difficulties Questionnaire (SDQ). Method: Parents and teachers of 1487 elementary school children (759 boys and 728 girls aged 6-12 years) participated in this study. Results: The results of confirmatory factor analyses of the parent and teacher versions of the SDQ supported the five-factor structure reported in previous studies. However, factor invariance across sex was not observed. The alpha coefficients for the subscales of the SDQs varied between 0.55 and 0.86, the same reliability measures that were also reported in previous studies. Moreover, analyses of variance showed significant differences on all of the subscales according to sex and teacher-parent ratings. Conclusion: The factor structure of the SDQ was generally supported, but more gender-segregated investigations of the factor structures are needed. Parents tended to give higher ratings on the difficulties and strengths of children compared to the teachers. Boys were rated higher than girls were on difficulties, while girls were rated higher than boys were on strengths.