["Family Relations, EarlyView. ", "\nAbstract\n\nObjective\nThis study used a longitudinal actor–partner interdependence model to investigate how couples' difficulties in emotion regulation affect their subjective happiness through marital conflict.\n\n\nBackground\nEmotion regulation is central to marital quality and individual well‐being. However, few studies have longitudinally examined the reciprocal effects of spouses' emotion regulation difficulties on marital conflict and happiness.\n\n\nMethod\nLongitudinal data were drawn from 519 Korean married couples participating in the 13th (2020) and 15th (2022) waves of the Panel Study on Korean Children. Actor–partner interdependence models tested actor and partner effects of emotion regulation difficulties on subjective happiness, with marital conflict examined as a hypothesized intervening variable.\n\n\nResults\nActor effects showed that both husbands' and wives' difficulties in emotion regulation heightened their own perceptions of marital conflict and lowered their happiness. Partner effects indicated that each spouse's difficulties also increased the other's conflict perception, indirectly reducing the other's happiness. Husbands' regulatory difficulties had a stronger effect on their own conflict perception, whereas wives were equally influenced by their own and their husbands' difficulties. No direct partner effects on happiness were found.\n\n\nConclusion\nThis study demonstrates the dynamic interplay between spouses' difficulties in emotion regulation, marital conflict, and subjective happiness. The findings suggest that strengthening emotion regulation skills in both partners can be a practical strategy to alleviate marital conflict and enhance individual well‐being. Interventions and counseling programs that target emotion regulation may therefore play a key role in promoting healthier couple relationships and overall family functioning.\n\n"]