Studies document that parents serve as children’s primary socialization agents, particularly for moral development and prosocial behavior; however, less is known regarding parental influences on prosocial outcomes during the transition to adulthood. The purpose of this study was to investigate how mother–child relationship quality was related to prosocial tendencies via emerging adults’ regulation of prosocial values. Participants included 228 undergraduate students (ranging from 18 to 25 years; 90% European American) and their mothers (ranging from 38 to 59 years) from four locations across the United States. Path analyses using structural equation modeling revealed that mother–child relationship quality was related to emerging adults’ regulation of prosocial values, which was, in turn, related to emerging adults’ prosocial tendencies. Specifically, emerging adults who reported higher levels of internal regulation of prosocial values were more likely to report prosocial tendencies that de-emphasized themselves, and were less likely to report prosocial tendencies for the approval of others.