This study maps the perceived social support of youth in Israeli educational residential care settings (RCSs) from their nuclear and extended family, peers and RCS staff and their overall level of perceived social network sufficiency. Self-report questionnaires were completed by 864 adolescents in grades 8–12, residing in sixteen educational RCSs for youth from underprivileged backgrounds. The findings indicate that adolescents from divorced families and those born in certain countries other than Israel are at risk for poorer social network sufficiency. All youth rated their mother as the greatest source of support. However, the order of support levels from other sources varied according to the youths’ characteristics. For example, paternal support was perceived as second in importance by youth from married-parent families and by boys, but not by youth from divorced families and by girls, who rated peers as second in importance. The perceived support of both grandparents and RCS staff was lower than that of other sources, although they are still significant figures in youths’ lives. The findings may help identify groups of adolescents in RCSs who are vulnerable to poorer social support, which in turn can help design programmes strengthening their ties with potential support sources in their lives.