Little is known about the relationship between sport participation and body adaptations during growth. Our aim was to investigate whether soccer participation in youth is associated with the degree of genu varum. The design was a retrospective cohort study. Three hundred and thirty-six male soccer players, and 458 male non-soccer players (aged from 8 to 18) were recruited and included in the study. The intercondylar (IC) or intermalleolar (IM) distance were clinically measured with a specifically designed instrument. The results of this study revealed a statistically significant increase in degree of genu varum in both groups from the age of 14. However, at the age of 16–18 years a significant higher degree of genu varum was observed in the soccer players compared to the non-soccer players (P = 0.028). Intense soccer participation increases the degree of genu varum in males from the age of 16. Since genu varum predisposes to injuries, efforts to reduce the development of genu varum in male soccer players are warranted.