<p>Callous-unemotional traits are a risk factor for low prosocial behaviors and high bullying behaviors in adolescence. Although the interplay between adolescents’ callous-unemotional traits and their prosocial and bullying behaviors is theoretically expected, previous empirical studies have relied heavily on cross-sectional and between-person analyses, limiting the understanding of the within-person bidirectional associations between these constructs. Moreover, the underlying mediating mechanism between adolescents’ callous-unemotional traits and their prosocial and bullying behaviors remains unclear. To address these gaps, the current study investigated the within-person bidirectional associations among callous-unemotional traits, moral disengagement, prosocial behaviors, and bullying behaviors, and examined the mediating role of moral disengagement, using the random intercept cross-lagged panel model. A total of 2,407 Chinese adolescents (50.23% girls, <i>M</i>_age = 12.75, <i>SD</i> = 0.58 at baseline) were surveyed across three waves with one-year intervals. At the between-person level, these four constructs were significantly correlated. At the within-person level, partial bidirectional associations were observed among callous-unemotional traits, moral disengagement, and bullying behaviors. Callous-unemotional traits and moral disengagement had a unidirectional predictive effect on prosocial behaviors. Callous-unemotional traits indirectly predicted prosocial and bullying behaviors through moral disengagement, and bullying behaviors also indirectly predicted callous-unemotional traits through moral disengagement. These findings contribute to a comprehensive perspective on the dynamic interplay among callous-unemotional traits, moral disengagement, prosocial behaviors, and bullying behaviors, and highlight the importance of addressing moral disengagement as a key intervention strategy to foster prosocial behaviors and curb bullying behaviors in adolescence.</p>