[Purpose] This study examined sex differences in physical activity and social cognitive theory factors in Korean college students. [Subjects and Methods] A cross-sectional survey of 688 college students (285 men and 403 women) in Korea was conducted using a self-reported questionnaire. [Results] There was a significant difference in the level of physical activity between male and female students. The significant predictors of physical activity for male students were physical activity goals, physical activity self-efficacy, and sitting time. Meanwhile, those for female students were perceived weight, physical activity goal, physical activity outcome expectations, and sitting time. [Conclusion] Sex differences should be considered when developing interventions to increase physical activity.