The authors demonstrate that people differ systematically in their implicit theories of emotion: Some view emotions as fixed (entity theorists), whereas others view emotions as more malleable (incremental theorists). Using a longitudinal and multimethod design, the authors show that implicit theories of emotion, as distinct from intelligence, are linked to both emotional and social adjustment during the transition to college. Before entering college, individuals who held entity (vs. incremental) theories of emotion had lower emotion regulation self-efficacy and made less use of cognitive reappraisal (Part 1). Throughout their first academic term, entity theorists of emotion had less favorable emotion experiences and received decreasing social support from their new friends, as evidenced by weekly diaries (Part 2). By the end of freshman year, entity theorists of emotion had lower well-being, greater depressive symptoms, and lower social adjustment as indicated in both self- and peer-reports (Part 3). The emotional, but not the social, outcomes were partially mediated by individual differences in emotion regulation self-efficacy (Part 4). Together, these studies demonstrate that implicit theories of emotion can have important long-term implications for socioemotional functioning.