Psychological intimate partner violence (IPV) is a common occurrence during the transition to parenthood, with deleterious consequences to partners and young children. This study investigated longitudinal links between attachment insecurity, relationship dissatisfaction, and psychological IPV in a community sample of 98 heterosexual couples expecting their first child. Couples self-reported prenatal levels of attachment anxiety and avoidance, relationship satisfaction at 1-year postpartum, and frequency of psychological IPV perpetration and victimization at 2-years postpartum. Path analyses revealed evidence for mediation of the effects of men’s and women’s attachment anxiety and men’s avoidance on IPV via relationship dissatisfaction (though the bivariate association between women’s anxiety and their psychological IPV was nonsignificant). Men and women who reported greater attachment anxiety prenatally, as well as men who reported greater attachment avoidance, were less satisfied with their relationships at 1-year postpartum. Subsequently, those who were less satisfied perpetrated psychological IPV more frequently at 2-years postpartum. Further, an unexpected suppression effect was identified post hoc such that the direct association between men’s prenatal avoidance and their psychological IPV at 2-years postpartum became negative with the addition of the relationship dissatisfaction mediator. These results indicate that men’s and women’s attachment anxiety and men’s attachment avoidance during pregnancy increase the risk of postpartum psychological IPV through increases in relationship dissatisfaction; however, men’s attachment avoidance may actually decrease the risk of postpartum psychological IPV once relationship satisfaction is controlled for. Implications for prenatal interventions targeting relationship dissatisfaction to mitigate the risk of IPV are discussed.