Aggressive behaviors in youth tend to be relatively stable across the lifespan and are associated with maladaptive functioning later in life. Researchers have recently identified that both violence exposure and negative affective experiences are related to the development of aggressive behaviors. Children exposed to violence also often experience negative affect (NA) in the form of anxiety and depression. Bringing these findings together, the current study used a clinical sample of youth (N = 199; ages 7–17 years) referred to a psychiatric residential treatment facility to examine the specific contributions of NA and exposure to violence on the development of aggressive behaviors in youth. Using structural equation modeling, both NA and recent exposure to violence significantly predicted aggressive behaviors. More importantly, negative affect partially mediated the relationship between exposure to violence and aggression. Implications of these findings from a clinical perspective and future directions for research on aggression are discussed.