Saudi Arabia has one of the highest childhood obesity rates worldwide. The primary factor associated with the high prevalence of obesity among adolescents is a lack of physical activity (PA). Compared to male adolescents, very few Saudi female adolescents meet the World Health Organization recommendation of achieving 60 min of moderate to vigorous PA per day, putting them at a higher risk of overweight and obesity. This cross-sectional study aimed to examine the relationship between the theory of planned behavior and psychosocial factors, including attitude toward PA, subjective norms, perceived behavioral control (PBC), PA intention, and self-reported PA among Saudi female adolescents. A convenience sample of 329 Saudi female adolescents was recruited from all-female public intermediate and high schools in the Eastern Region of Saudi Arabia. Data were collected using online self-administered questionnaires. The theoretical model was examined using structural equation modeling. The findings revealed a higher prevalence of overweight compared to obesity among participants. About half the participants were from families with a medium monthly income. The mean PA score indicated a low level of PA. The model demonstrated significant explanatory power for both PA intention and PA behavior, respectively. The strongest predictor of adolescents' intention was attitude, followed PBC.Moreover, the female adolescents' attitudes and PBC had significant indirect effects on self-reported PA through intention, while intention had a direct effect on PA. The model did not support a direct or indirect relationship between subjective norms and PA. The findings provide essential support for targeting attitude and perceived behavior control of female adolescents in order to enhance their PA intention. This theoretical understanding can help design effective theory-based interventions that promote PA among Saudi female adolescents.