The study examined the intergenerational transmission of aggressive conflict resolution toward intimate partners from Generation 1 (G1) parents during Generation 2's adolescence to both G2 and their partners (G2 partner), and the potential spillover effects from G2 and G2 partner's aggressive conflict resolution to G2's harsh and inconsistent parental discipline towards Generation 3 (G3) children. Using data from the Research on Adolescent Development and Relationships (RADAR) project, G1, G2 (51.5% girls; Mage = 14.82 in mid-adolescence, Mage = 29.66 in parenthood), and later G2's partner and G3 were followed from G2's adolescence to adulthood. The sample comprised 1178 G1-G2 dyads, including 222 G1-G2-G3 triads. Path analyses provided evidence for (1) intergenerational transmission, that is, G1's aggressive conflict resolution in G2's mid-adolescence weakly predicted G2's aggressive conflict resolution in G2's adulthood and (2) spillover effects, that is, G2's aggressive conflict resolution predicted G2's harsh and inconsistent discipline toward G3 children. Most of the intergenerational transmission and spillover relations did not differ across G1 and G2 gender. Overall, the findings highlight the intergenerational transmission of aggressive conflict resolution towards intimate partners and its subsequent relation with harsh and inconsistent discipline. Future prevention could target both parental figures in G1 and G2 to disrupt the cycle of aggressive conflict resolution and prevent problematic discipline practices.