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Introduction & Objective: Participation in regular physical activity is associated with a variety of positive outcomes for young people. Physical activity (PA) rates decline precipitously during the high school years and are consistently lower among adolescent girls than among adolescent boys. In order to stop or diverse this negative trend, there are necessary interventions based on various theories and models to promote physical activity in girls. Materials & Methods: This randomized control study evaluated the effectiveness of a 24-week exercise education program based on Pender’s Health Promotion model to improve cognitive and psychosocial factors associated with physical activity and to promote physical activity in adolescent girls (n =106). The program included educational sessions and tailored counseling. Results: There was an increase of 45 minutes for daily physical activity in the experimental group compared to their baseline. After intervention, the training group had a positive significant progression in stages along with significant improvements in self efficacy, enjoyment of physical activity, interpersonal influences, planning for physical activity, and also a decrease in perceived barriers to physical activity and competing preferences (p ≤ .0001-0.04). Conclusion: Findings of this study showed the positive effect of program on stage of change and potential determinants of the behavior of physical activity. The high proportion of the people in action and maintenance in experimental group compared to the baseline and the attainment of recommend criteria for physical activity are promising findings of school-based intervention based on Pender’s health promotion model.