Purpose <p>To examine the effects of physical activity on college students' social physique anxiety and the mediating and moderating roles of negative physical self and mental toughness in it, and to provide empirical evidence that physical activity improves college students' social physique anxiety.</p> Methods <p>Stratified whole cluster convenience sampling was used to survey 1177 university students, 53.8% male and 46.2% female, with a mean age of (19.12 ± 1.21) years. Mediated and moderated effects were analysed using SPSS 26.0 and AMOS 28.0.</p> Results <p>(1) Physical activity negatively predicted social physique anxiety (2) Negative physical self and mental toughness (individual power) played a significant partial mediating role between physical activity and social physique anxiety, with mediating effects accounting for 40.09% and 27.11% of the total effect, respectively; (3) The R² change in the interaction term of physical activity and family support in mental toughness (supporting force) reached a significant level, and family support played a significant negative moderating role between physical activity and social physique anxiety, whereas the interaction term of interpersonal assistance and physical activity was not significant and could not moderate the interrelationship between physical activity and social physique anxiety.</p> Conclusion <p>Physical activity affects college students' levels of social physique anxiety through negative physical self and mental toughness (individual power); the effect of physical activity on social physique anxiety is negatively moderated by the family support dimension of mental toughness (supporting force).</p>