Narcissism and CU traits are two of the personality features of psychopathy. These personality features have each shown independent relations with aggression in adolescents, suggesting a tendency for youth characterized by such traits to engage in aggressive or violent interpersonal behaviors. Furthermore, family conflict has demonstrated its own relation with youth aggression. The current study sought to examine the potential additive effect of these constructs on aggression in a sample of 153 adolescents (130 males, 23 females) ages 16–18 enrolled in a voluntary military-style residential program. Results indicated that perceived marital discord heightened the risk of aggression for youth characterized by narcissism or CU traits. Adolescent reports of parent–child conflict exhibited a similar moderational effect. Thus, family harmony, or at least youth perceptions thereof, may be a worthy target of future intervention for youth with psychopathy-linked personality features, with more research needed on younger samples.