Emotion dysregulation emerges from an interaction between individual factors and environmental factors. Changes in biological, cognitive, and social systems that characterize adolescence create a complex array of environmental factors contributing to emotion dysregulation during this developmental period. In particular, peer victimization (PV) has long-term consequences for emotion dysregulation. Yet, previous research has also indicated that emotion dysregulation can be both an antecedent to and outcome of PV. The present study evaluated reciprocal associations between longitudinal changes within repeated measures of PV and emotion dysregulation across adolescence and into young adulthood. The sample included 167 adolescents (53% male, = 14.07 years at Time 1) who participated in a longitudinal study across five time points, with approximately 1 year between each assessment. Latent change score modeling was used to examine reciprocal associations between PV and emotion dysregulation. Results emphasize bidirectional associations between PV and emotion dysregulation. Consistent with social information processing theory, greater emotion dysregulation predicted greater relational and overt victimization over time. Moreover, higher overt victimization predicted increases in emotion dysregulation. Our results offer insights toward developmentally informed longitudinal, transactional models linking negative social environments, and emotion dysregulation development across adolescence and into young adulthood. (PsycInfo Database Record (c) 2024 APA, all rights reserved).