Spousal interactions are key predictors of relationship satisfaction in couples, but it is not yet sufficiently clear as to which aspect of spousal interactions matters most. In this study, three forms of interactions are examined to disentangle their unique associations with relationship satisfaction. Altogether, 1944 married individuals completed questionnaires in a cross-sectional study. Self-report measures of relationship external stress, negative interactions (NIs), positive interactions (PIs), dyadic coping (DC), and relationship satisfaction were assessed. A multigroup path analytical mediation model was used to test whether couple interactions mediate the association between stress and relationship satisfaction. Stress stemming from outside the relationship is highly associated with an increase in NIs and a decrease in DC. Although all interactions covaried significantly with relationship satisfaction, DC outperformed PI and NI. Being supported by the partner in times of need (i.e. after experiencing relationship external stress) seems to be particularly relevant for marital quality.