ABSTRACT Body image is an important area for everyone because it affects self-esteem. A positive body image has also been found to have the potential to reduce unhealthy dieting behaviors. People who are more likely to engage in healthy weight control are associated with high self-esteem. Therefore, it was to investigate the relationship between body image, diet behavior, and self-esteem, and the mediating role of diet behavior in the relationship between body image and self-esteem. The cross-sectional study collected data from 386 workers (211 male, 175 female) in their 20s and 40s living in Seoul and Gyeonggi-do, South Korea. Body image was found to significant influence on diet behavior and self-esteem. Diet behavior was also found to have a significant influence on self-esteem, and diet behavior appeared to play a partial mediating role in the relationship between body image and self-esteem. Diet behavior can vary depending on how one perceives the concept of diet and participates in healthy weight control, which may also affect self-esteem. Body image can also be an important source of self-esteem evaluation and emphasizes that diet behavior, which has shown a mediating role, introduces a positive challenge that contributes to self-esteem.