The present study examined responses to romantic breakup as a function of relationship contingency of self-worth (CSW)—the degree to which individuals base self-worth on being in a romantic relationship. Relationship CSW was hypothesized to be a vulnerability factor, exacerbating affective and behavioral responses to romantic relationship dissolution. Results of structural equation modeling (N = 312) revealed that among participants who reported a breakup over the past year, those who more strongly based self-worth on being in a relationship reported greater emotional distress and obsessive pursuit of their ex-partners than did those with lower relationship CSW. Specifically, emotional distress partially mediated the link between relationship CSW and obsessive pursuit. Implications of relationship CSW for interpersonal motivation and well-being are discussed.