Both psychopathology and aggression are heterogeneous constructs. Determining which forms of psychopathology relate to risk for different classes of aggressive behavior has implications for risk recognition and management. This study examined the relationships of impulsive aggression (IA) and proactive aggression (PA) to psychopathy and symptoms of several Diagnostic and Statistical Manual Axis I disorders in a sample of criminal offenders. Results replicated prior findings from community samples of a broad relationship between psychopathology and IA. PA was related only to psychopathy. An interaction was found whereby IA was associated with impulsive-antisocial traits of psychopathy only for individuals with moderate to high levels of generalized anxiety. Results indicate that assessing and treating several Axis I disorders in offenders may decrease risk for IA. Moreover, current findings raise the possibility that generalized anxiety is a key, modifiable component of the relationship between IA and impulsive-antisocial traits.