This study examined how the combination of sibling victimization and parental child maltreatment is related to mental health problems and delinquency in childhood and adolescence. Co-occurrence, additive associations, and interactive associations of sibling victimization and parental child maltreatment were investigated using a sample of 2,053 children aged 5-17 years from the National Survey of Children's Exposure to Violence. The results provide primarily evidence for additive associations and only suggest some co-occurrence and interactive associations of sibling victimization and child maltreatment. Evidence for co-occurrence was weak and, when controlling for the other type of maltreatment, only found for neglect. Sibling victimization was related to more mental health problems and delinquency over and above the effect of child abuse and neglect. Moderation by sibling victimization depended on child age and was only found for the relation between both types of child maltreatment by parents and delinquency. For mental health, no interactive associations were found. These results highlight the unique and combined associations between sibling victimization on child development.