Whether people believe their romantic relationship quality can be improved or not could largely influence the relationship consequences. However, relatively fewer studies have focused on the potential factors that account for the association between such beliefs and romantic relationship satisfaction (RS). In the current research, we aimed to investigate the relation between implicit theories of relationships (ITRs) and RS and the potential moderating role of perceived partner responsiveness (PPR) in such relation. An online survey was administered to 300 Chinese young adults (aged 18–35) who were currently in romantic relationships, measuring their implicit beliefs about romantic relationships, PPR, and RS. Results indicated that (a) growth beliefs of ITRs and PPR were positively associated with RS, respectively; (b) destiny beliefs of ITRs were not significantly associated with RS; and (c) PPR moderated the relation between growth beliefs of ITRs and RS. Growth beliefs were significantly positively correlated with RS in lower PPR conditions but not in higher PPR conditions. We further discussed the theoretical and practical implications of these results.