Stress originating within one’s relationship (internal stress), such as conflicts between partners, has been shown to have detrimental effects on relational longevity and well-being. Theoretical arguments suggest the need to examine the impact stress originating outside the relationship (external stress) can have on relational well-being. External stress can spillover into the relationship causing internal stress, making stress a dyadic versus individualistic phenomenon. Using data from 131 couples, we examined whether internal stress may mediate the association between external stress and relationship satisfaction and how dyadic coping may moderate this relationship within one year. Dyadic coping was found to decrease the impact of chronic external stress on chronic internal stress, particularly in women. Women who reported higher dyadic coping skills had a higher relationship satisfaction which influenced also their partner’s relationship satisfaction positively. Further research should focus on couples’ dyadic coping skills as a mechanism between stress and relationship satisfaction.