© 2015, Springer Science+Business Media New York. Childhood aggression often precedes more costly problem behavior that may result in psychiatric hospitalization. Further understanding of the link between proactive and reactive functions of aggression and psychiatric problems would be useful for refining current prevention efforts and ultimately help reduce the number of hospitalizations. The current study examined parenting styles, gender, and age as potential moderators of the link between the proactive and reactive functions of physical aggression and more severe externalizing symptomatology [i.e., oppositional defiant disorder (ODD) and conduct disorder (CD) symptomatology]. Participants included 392 children ages 6–12 years of age (M = 9.4, SD = 1.9) admitted consecutively to a psychiatric inpatient facility. Results indicated that both proactive and reactive aggression were associated with both ODD and CD symptoms. However, parenting styles were most influential on the association between proactive aggression and ODD symptoms for females and older children. Implications and future directions are discussed.