Personal goals, that is, ideas of what one wants to maintain, attain, or avoid in the future, are pursued within social contexts and may influence the social systems a person belongs to. Focusing on romantic partnerships as one of the most important social contexts in adulthood, this longitudinal study investigated the role of partners' mutual goal knowledge for partnership development (T1: N =69 couples; T2: N =47). Partners described their own personal goals and the goals they assumed their partners to have. Trained coders rated the overlap between the self-reported and the ascribed goals. Actor–partner interdependence models showed that knowing one's partner's goals was associated with a higher level of partnership satisfaction after about 16 months, controlling for initial partnership satisfaction. Having a partner who knows one's goals, by contrast, predicted greater feelings of closeness to that partner after the same period of time, controlling for initial levels of closeness; and this association could not be attributed to a greater similarity between both partners' goals. Overall, this research shows that both the ‘I know you’ and the ‘You know me’ components contribute to positive partnership development, and that their specific implications vary for different facets of partnership quality.