Purpose. This study was done to determine the effects of weight management program using self-efficacy in middle-aged obese women. The study also attempted to measure the effects of the program on the weight efficacy lifestyle, body composition, and depression. Method. The research design of this study was a nonequivalent control group pretest-posttest design. The experimental group consisted of 21 middle-aged obese women and another 21 middle-aged obese women in the control group. The women in the experimental group participated in the weight management program for 12 weeks using self-efficacy. The weight management program using self-efficacy included education on effects of exercise for weight control, aerobic exercise program, muscle training and counseling through the telephone. Results. After 12 weeks of participation in the program, BMI (p <.0001), body fat % (p <.0001), abdominal fat (p <.0001), in the experimental group were significantly decreased compared to the control group. Weight self-efficacy lifestyle (p <.0001) and depression (p =.006) in the experimental group were significantly improved after the program compared to the control group. According to these findings, weight management program self-efficacy for middle-aged obese women could increase weight efficacy lifestyle, and decrease depression, BMI, body fat, and abdominal fat. Conclusion. The result also suggested that the increasing weight efficacy and lifestyle help the obese women to perform and continue exercise. This program could be used in the community such as public health center for weight care and mental health promotion of middle-aged obese women.