This study examined associations of best friend and peer group aggressive characteristics with students' overt and relational aggression, and whether coolness moderated these associations across the fall and spring of the first year in middle school. Students (N = 174; 57% females) self-reported best friendship and peer group members, as well as peer-nominated coolness and aggression (overt, relational). Results indicated positive relations of best friend and peer group aggressive characteristics with subsequent aggression, and that coolness moderated these associations. Specifically, non-cool youth had higher levels of subsequent overt and relational aggression with aggressive best friends, but lower levels of later relational aggression when in relationally aggressive peer groups. In contrast, cool youth had lower levels of subsequent relational aggression with relationally aggressive best friends, but higher levels of later relational aggression when in relationally aggressive peer groups. Implications for examining multiple peer contexts and coolness during early adolescence are discussed.