Weight reduction behavior is common among adolescent girls. The present study examined the status of weight reduction behavior and factors affecting the behavioral intention of weight reduction using the Health Belief Model (HBM) for female middle school students by weight category. Survey data was collected from three girl's middle schools in Gyeongju, Korea. A total of 299 female middle school students participated in this study. The questionnaire had questions about general characteristics, weight reduction behavior, and variables of HBM (perceived threat, perceived benefits, perceived barriers, cues to action, self-efficacy in dietary life and exercise, and behavioral intention of weight reduction). Descriptive statistics, Chi-square tests, ANOVA, and multiple regression analysis were applied to analyze the variables. A higher percentage of students in the overweight group attempted weight reduction than those in the underweight and the normal weight groups (P < 0.001). Among students who had attempted weight reduction, 73% tried diet therapy, while 78% tried exercise. Students in the normal and overweight groups showed significantly higher threat (P < 0.01) and cues to action (P < 0.001) than those in the underweight group. As for perceived benefits, barriers, and self-efficacy in dietary life and exercise, there were no significant differences among weight groups. Students in the overweight group showed the strongest intention of weight reduction and there were significant differences among the three weight groups (P < 0.001). Perceive threat (P < 0.01), cues to action (P < 0.001), and perceived self-efficacy (P < 0.01) were significantly associated to behavioral intention of weight reduction for all respondents. For the underweight group, perceived threat (P < 0.05) and perceived self-efficacy (P < 0.01) were the significant variables. For the overweight group, cue to action was the significant variable (P < 0.05).