We describe adolescents' perpetration of sibling aggression and its link to physical health two years later. In-school surveys at Time 1 (N = 331) and Time 2 (two-years later, N = 283) were administered to adolescents (at Time 1, Mage = 15.71 years, SD = .63; 52% female) living in the United States querying about perpetration of aggression toward a sibling closest in age and perceived physical health. The majority of adolescents perpetrated aggression towards their sibling (74%). Adolescents who were part of brother-brother pairs reported the most aggression. Hierarchical regression analysis showed that perpetrating sibling aggression more often at Time 1 was predictive of lower physical health at Time 2 controlling for Time 1 physical health and demographic characteristics. Perpetration of aggression toward a sibling is common and has negative health consequences in late adolescence suggesting this issue should be targeted to improve adolescents' sibling dynamics and physical health.