Microcontextual factors (i.e., contextual characteristics of the specific victimization incident) may help to explain the association between adolescents' daily peer victimization experiences and well-being. In the present study, daily report methodology was used to assess sixth (N = 150; 53% girls) and ninth grade (N = 150; 50% girls) students' current well-being and peer victimization earlier in the day on 5 random school days within a 2-week period. Associations between peer victimization microcontextual factors (number of aggressors, presence of witnesses, and receipt of help) and fluctuations in adolescents' daily well-being (humiliation, worry, and physical symptoms) were examined in an ethnically diverse sample of White, Latino, Asian, African American, and multiethnic students. Humiliation increased on days in which students reported public victimization, multiple aggressors, and no help. Worry increased on days students experienced private victimization and when boys (but not girls) experienced private victimization, victimization by a single aggressor, and received peer help. Physical symptoms were higher on days that victimization occurred, regardless of context, but only for sixth graders and not ninth graders. These findings suggest that the victimization microcontext can offer insight about the types of peer victimization exposure that might produce the greatest daily risk for adolescents.