This study tested two hypotheses about gender-specific mental health effects of peer stressors during early adolescence: (1) boys and girls are sensitive to different types of peer stressors, and (2) peer stress is associated with different mental health problems in boys and girls. These two hypotheses were tested in a prospective large population cohort of 2084 Dutch young adolescents. Internalizing and externalizing problems were measured at baseline and follow-up, while stressful life events in the period between baseline and follow-up were measured retrospectively at follow-up. We performed the analyses with two types of peer stressors; victimization at school and relationship losses. Relationship losses were more strongly associated with internalizing and externalizing problems in girls than boys, supporting the first hypothesis. Peer victimization at school was also associated with both types of mental health problems, but equally strong in both genders. Peer stress is unlikely to be associated with different mental health problems in boys and girls. Instead, boys and girls are more likely to be susceptible to different types of peer stressors.