Objectives: The purpose of this study was to evaluate the effects of the Tai Chi exercise and combined behavior therapy on body composition, blood lipids level and self efficacy in obese middle-aged women. Methods: A quasi-experimental design was used. Subjects were 63 middle-aged women whose body mass index (BMI) is over 25 kg/m². A pretest-posttest design was used with the experimental group (n=30) who participated in the Tai Chi combined with behavior therapy for 12 weeks, and the control group (n=33) who did not. Results: The experiment group showed significant decreases in waist circumference, body weight, BMI, Waist-hip ratio, and diastolic blood pressure. Moreover, the experiment group showed significant decreases in Total cholesterol (TC), Triglycoride (TG), and increase in High lipoprotein cholesterol (HDL-C) compared to the control group. The self efficacy was significantly improved for the experimental group compared to the control group. Conclusions: This study was provided an evidence that Tai Chi combined with behavior therapy can be useful to manage body composition, blood lipid profiles for obese middle-aged women.