Background: Physical activity has multiple health benefits, yet its association with female fertility remains unclear. Considering the critical effects of lifestyle on reproductive health, this study aimed to compare the physical activity and body composition of fertile and infertile women in Arak during 2021. Methods: This study is a case-control study that was performed on 200 fertile and infertile women (20 to 40 years old) referred to the infertility center in Arak who was selected through the convenience sampling. Participants completed self-administered questionnaires on sociodemographic and lifestyle characteristics, physical activity and sedentary behavior. Anthropometric characteristics and body composition were also measured. Multivariable logistic regression was used to analyze the association of fertility with physical activity level, sedentary behavior and body composition. Results: The level of physical activity (P=0. 001) and body mass index (P=0. 03) in infertile women were lower and higher compared to fertile women, respectively. In women with moderate level of physical activity (odds ratio 4. 42 and 95% confidence interval: 1. 60, 12. 99 and P=0. 004) the chance of infertility decreases. Women who spend more than 300 minutes a day sedentary are 2. 07 times more likely to have fertility problems than women who are physically active (odds ratio 2. 07 and 95% confidence interval: 1. 36, 3. 14 and P=0. 001). Conclusion: This study shows that low physical activity, sedentary lifestyle and obesity are independent risk factors associated with infertility, so to prevent and even treat infertility, more attention should be paid to lifestyle behaviors in women.