Additionally, targeted interventions should be designed, which include strategies and methods, especially for girls. However, no study has been done specifically to increase physical activity among Thai adolescent girls. Thus, in order to fill the gap of knowledge on the effectiveness of intervention programs, in promoting physical activity among Thai adolescent girls, the purpose of this study was to determine the effects of a physical activity promotion program on perceived self-efficacy (PSE), physical activity (PA) and physical fitness (PF) of Thai adolescent girls.