Introduction:Lifestyle improvement is one of the main strategies to increase treatment persistence in breast cancer survivors. The purpose of the present study was to determine the effect of a light-intensity physical activity program on Socio-cognitive factors that affect sedentary behavior and lifestyle in breast cancer survivors in Isfahan city.Methods: Twenty-four female breast cancer survivors were recruited via convenience sampling and randomly assigned to experiment and control groups (12 subjects for each group). Both groups were assessed using Busschaert's context-specific sedentary behavior questionnaire and the Miller-Smith Lifestyle Assessment Inventory before and after the intervention. The light-intensity physical activity program was conducted for one month in the experimental group based on Australia's Physical Activity and Sedentary Behavior Guidelines for Adults. Data were analyzed using descriptive statistics including mean and standard deviation and inferential statistics including ANCOVA and MANCOVA with a significance level of 0.05. Results:There was a significant difference between the two groups in lifestyle and Sociocognitive factors affecting sedentary behavior (except for the sedentary behavior modelling) (p= 0.001). Conclusion:It seems that performing light physical exercises may improve the lifestyle and Socio-cognitive factors affecting sedentary behavior by changing key factors such as motivation and intrapersonal relationship in breast cancer survivors.