Evidence on the intergenerational continuity of intimate partner violence (IPV) suggests small to moderate associations between childhood exposure and young adult IPV involvement, suggesting an indirect effects model. Yet, few prospective studies have formally tested meditational mechanisms. The current study tested a prospective (over 9 years) moderated-mediational model in which adolescent psychopathology symptoms (i.e., internalizing, externalizing, and combined) mediated the association between exposure to IPV in middle childhood and young adult IPV perpetration. In a more novel contribution, we controlled for proximal young adult partner and relationship characteristics. The sample consisted of n = 205 participants, who were, on average, assessed for exposure to parent IPV at age 12.30 years, adolescent psychopathology symptoms at age 15.77 years, and young adult IPV at 21.30 years of age. Data suggest a small, significant direct path from IPV exposure to young adult perpetration, mediated only through adolescent externalizing. Gender moderation analyses reveal differences in sensitivity to exposure across developmental periods; for males, effects of exposure were intensified during the transition to adolescence, whereas for females, effects were amplified during the transition to adulthood. In both cases, the mediational role of psychopathology symptoms was no longer significant once partner antisocial behavior was modeled. Findings have important implications for both theory and timing of risk conveyance.