The current study examined the association between playing high school football and involvement in violent behaviors in sibling pairs drawn from the National Longitudinal Study of Adolescent Health (Add Health). The analysis revealed that youth who played high school football self-reported more violence than those youth who did not play football. Quantitative genetic analyses revealed that 85% of the variance in football participation was the result of genetic factors and 62% of the variance in violent behavior was due to genetic factors. Additional analyses indicated that 54% of the covariance between football participation and violence was due to genetics and 46% was the result of nonshared environmental influences. However, even after controlling for genetic influences, participation in football appeared to increase violent behavior.