Social support by family, friends and significant others is known to buffer the impact of adverse life events on children's well-being and functioning, however little is known about pathways explaining this association. We investigated whether maltreatment-related cognitions mediate the association between social support and posttraumatic stress symptoms (PTSS). Furthermore, age was introduced as moderator. We assessed the history of maltreatment in 200 maltreated children and adolescents (age 8-17 years) using a semi-structured interview. Participants' perceived current social support, maltreatment-related negative cognitions related to the subjectively "worst" experience of maltreatment and PTSS during the past month were assessed using self-report questionnaires. A set of mediation analyses demonstrated, that negative maltreatment-related appraisals mediated the relation between perceived social support and PTSS. The hypothesized negative associations of social support with PTSS and dysfunctional cognitions did not differ between children (8-11:11 years) and adolescents (12-17;11 years). Thus, the protective function of social support after maltreatment can be explained by fewer negative beliefs maltreated youth have about themselves and the world. These results provide support to models of social-cognitive processing and emphasize the importance of cognitive coping in regard to episodes of maltreatment which can be shaped within social interactions with non-abusive caregivers, friends, and significant others. (C) 2016 Elsevier Ltd. All rights reserved.