Purpose: The purpose of this study was to determine the effects of smartphone apps applying BodyThink program on BMI, percentage ofbody fat, skeletal muscle rate, body image, and self-esteem of adolescent girls. Methods: Sixty-eight high school girls with a BMI of over25kg/m2 were recruited to participate in this study. Girls from four schools were divided into two groups: the experimental group, whichused the smartphone apps applying BodyThink program, and the control group, which used smartphone apps and small group counseling. The experimental group received the BodyThink program 6 times, scheduled once a week, with each session lasting 40~50 minutes. Testmeasures were completed before and after the 6 week intervention period for all participants. Collected data was analyzed using Shapiro-Wilk test, descriptive statistics, χ 2 test, independent t-test, Mann-Whitney U test with the SPSS/WIN 18.0 program. Results: The girls in theexperimental group significantly improved their results in BMI(Z=-1.67, p =.042), percentage of body fat (Z=-3.01, p =.001), skeletal musclerate (t=-3.50, p qqqlt;.001), and self-esteem (t=2.66, p =.005) after the program, compared to the girls in the control group. Conclusion: Mobileapplications applying psychological and emotional intervention programs have the potential to be effective alternative methods to improvethe body composition and self-esteem of obese adolescent girls.