A common view is that self-harmers are individuals who are exposed to or have been exposed to stressors and hostility in everyday settings. A strand of research has also found that self-harmers expose other people to their hostility. Extending these findings, this study examined whether adolescent self-harmers are simultaneously exposed and expose others to hostility in their everyday interpersonal contexts—at home, at school, and during leisure-time. The participants were 1,482 adolescents, ranging from 13 to 16 years of age, who attended different schools in a medium-sized city in central Sweden. The results show that the adolescents involved in mutually hostile relationships in their different interpersonal contexts exhibited higher self-harm than the adolescents who were exposed to others’ hostility or exposed other people to their hostility. Also, the more mutually hostile settings the adolescents were involved in, the more self-harm they reported. Overall, our findings suggest not only that selfharmers are exposed to hostility in their different interpersonal contexts, as has been typically assumed, but also that they simultaneously expose others to hostility in these contexts. This has implications for our understanding of young people who harm themselves and also for intervention.