This study investigated mothers’ attributions for children’s and adolescent’s transgressions towards their friends and younger siblings. Specifically, we examined (1) the types of attributions mothers make for their child’s harming behavior at different ages, (2) the types of attributions mothers make for children’s harming behavior across two relationship contexts (sibling and friend), and (3) if age-related changes in attributions about hurting friends are similar to, or different from, age-related changes in attributions about hurting siblings. A total of 101 children and adolescents were privately asked to nominate a time when they hurt or upset their younger sibling and friend (order counterbalanced). After the mothers and children conversed about these specific events, the mothers were privately asked a series of follow-up questions about their interpretations of these harming instances. Results indicated that mothers made different attributions in response to their children’s transgressions against their friends and siblings. Mothers more frequently made attributions of agent causality, intentional behavior, intentional harm, provocation (externality), stable relationship history, and consistent behavior when discussing conflicts with siblings. In contrast, when discussing conflicts with friends, mothers more frequently made attributions of externality (peer-related influences), event specificity, and unintentional harm. Unexpectedly, there were no significant main effects of the child’s age on mothers’ attributions. Overall, the findings elucidate how parents’ interpretations are situated within children’s distinctive relationship contexts (siblings and friends). Implications for parenting and child socialization are discussed.