Romantic relationships unfold in the context of people’s other interpersonal relationships, and processes that occur in those other relationships have been shown to affect the functioning of romantic relationships. In accordance with this perspective, two dyadic daily report studies demonstrated that people generalize experiences of interpersonal acceptance and rejection from other people onto their romantic partners. Participants felt more confident that they were valued by their romantic partners on days they experienced acceptance, relative to rejection, from outsiders. In addition, this overgeneralization of daily extradyadic acceptance and rejection had prospective effects on romantic relationship security the following day, was independent of the romantic partner’s actual relationship evaluations on each day, was partially mediated by daily self-esteem, and predicted daily enactment of prosocial and antisocial behaviors toward romantic partners. These results suggest that overgeneralization of daily acceptance and rejection from outsiders shapes the functioning of romantic relationships.