The study examined the effect of the TTM-based physical activity program on BMI, physical activity levels, and psychological in obese women. Thirty eight obese women participated in the 16-week physical activity program. During this period, the study participants’ BMI, physical activity levels, self-efficacy, and perceived benefits and barriers were measured at the three time point. Results indicated that obese women’ BMI significantly decreased and physical activity significantly increased over the program. In addition, exercise self-efficacy and perceived benefits significantly increased but perceived barriers of physical activity gradually decreased over the intervention. This study suggests that it is important to consider not only physical itself, but also the various psychological variables when planning and implementing the weight control program.