<p>Adolescence is marked by rapid psychosocial changes and a heightened risk for psychological disorders. Utilizing three waves of panel data from early adolescents in central China (<i>N</i> = 351, 47% boys, mean age = 13.66 years; six-month intervals), the current study applied latent growth modeling to examine developmental trajectories of emotional reactivity, internalizing problems, externalizing problems, and peer victimization, as well as their interrelations. After confirming measurement invariance across time, analyses revealed that all four constructs showed linear declines over time. Higher initial levels and slower declines in emotional reactivity significantly predicted higher initial levels and slower declines in both internalizing and externalizing problems. The data further showed that the initial level of peer victimization moderated these relationships: greater initial peer victimization amplified the association between emotional reactivity and internalizing problems, while accelerating reductions in peer victimization strengthened the coupling between decreases in emotional reactivity and decreases in externalizing problems. These findings integrate emotional dynamics, developmental cascades, and stress-sensitivity frameworks to highlight peer victimization as a critical contextual factor in adolescent psychological adaptation. Implications include the value of school- and family-based efforts to reduce peer victimization in order to enhance the benefits of interventions targeting emotional reactivity.</p>