--- - |2+ Abstract Objective Due to the unique importance of parental and sibling relationships and concurrently existing developmental challenges, the loss of a parent or sibling due to cancer is a highly stressful event for children and adolescents. This is the first systematic review that integrates findings on psychosocial outcomes after parental or sibling cancer bereavement. Methods A systematic search of Web of Science, PubMed, PsycINFO, and PubPsych was conducted, last in December 2017. Quantitative studies on psychosocial outcomes of children and adolescents who lost a parent or sibling due to cancer were included. Results Twenty‐four studies (N = 10 parental and N = 14 sibling bereavement), based on 13 projects, were included. Ten projects had cross‐sectional designs. Only 2 projects used large, population‐based samples and nonbereaved comparison groups. Outcomes were partially measured by single‐item questions. Bereaved children and adolescents showed similar levels of depression and anxiety compared with nonbereaved or norms. Severe behavioral problems were found rarely. However, in 2 large, population‐based studies, about half of the bereaved individuals reported unresolved grief. Bereaved adolescents had a higher risk for self‐injury compared with the general population in one large, population‐based study. Communication with health‐care professionals, family, and other people; social support; distress during illness; age; gender; and time because loss were associated with psychosocial bereavement outcomes. Conclusions Results indicate a high level of adjustment in cancer‐bereaved children and adolescents. A modifiable risk factor for adverse psychosocial consequences is poor communication. Prospective designs, representative samples, and validated instruments, eg, for prolonged grief, are suggested for future research. - Psycho-Oncology, Volume 27, Issue 10, Page 2327-2338, October 2018.