["Family Relations, EarlyView. ", "\nABSTRACT\n\nObjective\nUsing eight waves of South Korean longitudinal data, this study examined between‐couple and within‐couple associations in marital conflict and whether these associations differed between first‐time and experienced parents.\n\n\nBackground\nAlthough longitudinal studies have examined spousal exchanges of marital conflict across a limited number of timepoints, few have distinguished between‐couple from within‐couple effects or tested whether these dynamics vary by prior parenting experience.\n\n\nMethod\nAnnual longitudinal dyadic data were drawn from 2,072 South Korean heterosexual couples followed after the birth of the target child; baseline mean ages were 31.34 years for mothers and 33.89 years for fathers. Cross‐lagged panel models and random‐intercept cross‐lagged panel models were estimated.\n\n\nResults\nMothers' and fathers' average marital conflict was strongly and positively associated at the between‐couple level. At the within‐couple level, cross‐partner associations were unidirectional at earlier and middle timepoints and became bidirectional at later timepoints. No significant differences emerged between first‐time and experienced parents at either level.\n\n\nConclusion\nFindings underscore the cyclical and interdependent nature of marital conflict from childbirth through early childhood and the value of couple‐focused intervention.\n\n\nImplications\nDyadic interventions after childbirth may help prevent escalating marital conflict across early parenthood.\n\n"]