Implicit theories of relationships (ITRs) influence goals, motivations, attributions, and behavior in romantic relationships. We developed a model of ITRs that draws from social cognition, motivation, and achievement literatures, and derived conceptual parallels and hypotheses with regard to relationships. It is proposed that ITRs reflect the belief component of a larger system of motivations and goals that can influence the degree to which people are oriented toward the evaluation and cultivation of relationships. Research on ITRs is reviewed with regard to how they moderate well-documented associations between relationship perceptions and outcomes. Differences between ITRs and implicit theories in other domains are also discussed.