Previous research shows a link between the sense of relational entitlement and various couple outcomes. However, the mechanisms linking these variables are less discussed. With this study, the aim was to test the associations between individuals’ excessive and restricted sense of relational entitlement and their levels of couple satisfaction and conflict. In addition, it was tested whether the use of different negotiation tactics (cooperative and competitive) mediated the links. Six hundred and eighty-seven adults (55.2% women) participated in this study. Mediation analyses showed that a restricted sense of relational entitlement is associated with couple satisfaction and conflict through higher competitive negotiation use. Additionally, an excessive sense of relational entitlement is linked with couple satisfaction and conflict through lower cooperative negotiation use. This study has important implications for couples therapy addressing satisfaction issues, showing why and when educating couple interactions, especially those regarding negotiation, can improve relational functioning. Additionally, one’s relational well-being is strongly related to one’s mental health, and the applicability of the findings can be extended to all outcomes of the therapeutic process.