<p>While the link between aggression and internalizing concerns is well-established, additional work is needed to understand when these links are most pronounced, particularly by evaluating the intersection of how and why one aggresses. Variables that might buffer such associations, such as peer and family belonging, also warrant investigation. Data from 243 middle school students (<i>M</i>_<i>age</i> = 12.22; 46.5% female) were collected to evaluate the unique and interactive influences of the various forms and functions of aggression and family and peer belonging on symptoms of anxiety and depression. Results indicated that the link between aggression and internalizing concerns varies based on the form and function of aggression. Specifically, reactive overt aggression and peer belonging were uniquely linked to symptoms of both depression and anxiety. Family belonging was uniquely associated with depression. Proactive functions of aggression were not significantly associated with internalizing symptoms. Both family and peer belonging moderated reactive aggression-anxiety links, but not depression. In general, low levels of belonging were associated with high levels of anxiety regardless of levels of reactive aggression. The lowest levels of anxiety were evident at low levels of aggression and high levels of belonging. However, high levels of belonging did not buffer the links between aggression and anxiety. Findings underscore the importance of examining aggression using a more differentiated approach; they also highlight the relevance of belonging in understanding reactive aggression-anxiety links among middle school youth.</p>