AbstractCoronary artery disease (CAD) is the most common cardiovascular disease and the main cause of mortality in developing countries. Since physical activity and nutritional behaviors are modifiable risk factors in people at risk of CAD, the present study aims to explore the effect of an intervention based on the social cognitive theory (SCT) on physical activity and nutritional behaviors in middle-aged population at risk of CAD in the city of Bandar Abbas. The present cross-sectional study was conducted on 519 middle-aged subjects who visited the healthcare centers in Bandar Abbas, southern Iran, in 2023. The sampling was simple randomization. The data were collected using the general physical activity questionnaire, nutritional behavior questionnaire and a questionnaire based on the social cognitive theory (SCT). Descriptive statistics were used to describe the demographic features of the sample. Pearson correlation coefficient was used to test the relationship between the variables of study. Multiple linear regression was used to test the effect of the SCT constructs on physical activity and nutrition behaviors. All statistical analyses and hypothesis testing were done in SPSS 21, at a significance level of 0.05. A total number of 519 subjects participated in this study, whose average age was 44.23 ± 7.14 years. The results of Pearson correlation test showed a statistically significant positive correlation between nutritional behaviors and the constructs of self-efficacy, collective efficacy, outcome expectations, observational learning, normative beliefs, barriers and opportunities, reinforcement and punishment, and behavioral intention. There was also a significant positive correlation between physical activity and self-efficacy, normative beliefs, social support and behavioral intention. Social support, self-efficacy, normative beliefs, observational learning, behavioral skills and knowledge were found to be the predictors of physical activity. Reinforcement and punishment, normative beliefs, collective efficacy, social support and barriers and opportunities were the predictors of nutritional behaviors in the middle-aged population. As the results of the study showed, it is suggested to increase physical activity in the middle-aged population at risk of CAD using appropriate strategies to strengthen social support through family and friends, improve self-efficacy, identify positive and negative normative beliefs. Plans should be made to improve observational learning, increase behavioral skills, and increase knowledge to improve nutritional behaviors, use appropriate strategies to provide timely and appropriate rewards and punishments, identify and strengthen positive normative beliefs, improve collective efficacy, and increase social support. To this aim, families and other individuals around the middle-aged population can help remove barriers and create opportunities.