Research Findings: The transition to kindergarten has important ramifications for future achievement and psychosocial outcomes. Research suggests that physical aggression may be related to difficulty during school transitions, yet no studies to date have examined the role of relational aggression in these transitions. This article examines how engagement in preschool physical and relational aggression predict psychosocial adjustment during the kindergarten school year. Observations and teacher reports of aggression were collected in preschool, and kindergarten teachers reported on student-teacher relationship quality, child internalizing problems, and peer acceptance in kindergarten. Results suggested that preschool physical aggression predicted reduced peer acceptance and increased conflict with the kindergarten teacher. High levels of relational aggression, when not combined with physical aggression, were related to more positive transitions to kindergarten in the domains assessed. Practice or Policy: These data lend support to the need for interventions among physically aggressive preschoolers that target not only concurrent behavior but also future aggression and adjustment in kindergarten. Thus, educators should work to encourage social influence in more prosocial ways among aggressive preschoolers.