Purpose: This study was done to examine not only the relationships between body mass index (BMI), self-esteem, body image dissatisfaction (BID) and mental health, according to gender, but the mediating role of BID on mental health in relation to BMI and self-esteem among early adolescents. Methods: Data from 576 (296 boys and 280 girls) elementary school students in grades 5 to 6 were collected. A multiple-group path analysis was utilized to examine the relationships between BMI, self-esteem, BID and mental health by gender. Results: In the path analysis for all students, poor mental health was related directly to BID, while it was indirectly related to BMI and self-esteem. In the multiple-group path analysis of both genders, BID was found to have a significant direct and indirect effect on mental health for girls alone. Conclusion: The findings suggested that BID should be examined early to prevent poor mental health in early adolescent girls. This study helps to elucidate the role of early adolescent BID on mental health and provides insight for further prevention and intervention programs in school and community mental health settings.