Research Findings: This study investigated the long-term interrelations among children's language competencies, their home literacy environment (HLE), and 3 aspects of socioemotional development from ages 3 to 8, controlling for characteristics of the child and family. For this sample of 547 typically developing German children, parents and teachers reported on cooperative behavior, physical aggression, and emotional self-regulation. Language was assessed using established test instruments. HLE was operationalized by the number of books in the household, the frequency of shared book reading, and an observation during shared book reading. Path analyses supported effects of language and HLE at age 3 on all 3 indicators of socioemotional development over the 5-year period. An additional mediational analysis revealed different patterns of results depending on the aspect of socioemotional competency under study. Although the effect of early language and HLE at age 3 on cooperative and (low) aggressive behavior at age 8 was partially mediated by language at age 5, children's early language at age 3 was the best predictor of the development of emotional self-regulation. Practice or Policy: Findings identify a rich HLE and proper language skills as protective factors for socioemotional development in not-at-risk children; these factors should be further established in social skills training.