The purpose of this study was to investigate the effects of body weight, perception of body shape and satisfaction with body shape on obesity stress and self-esteem among middle school students. The participants in this study were 446 middle school students in K-city. The major results of this study are as follows. First, male students demonstrated higher obesity rates than female students, and female students considered themselves to be fatter and less satisfied with their body shape than male students. Female students had significantly more obesity-related stress than male students. Second, there were significant differences in physical obesity stress according to body weight status among male and female students, and there was statistically significant difference in psychological obesity stress according to body weight status among male students. Male and female students who considered themselves to be fatter and less satisfied with their body shape suffered from high obesity stress. Third, there was no significant difference in self-esteem according to body weight status, but self-esteem was affected by perception and satisfaction of body shape; male and female students who considered themselves to be fatter and less satisfied with their body shape showed low levels of self-esteem. As the result of regression analysis, psychological obesity stress was the strongest factor in explaining self-esteem among all students, and satisfaction of body shape was also found to be a significant variable among female students.