ObjectiveBreast cancer is the most common cancer diagnosis among women. The acute crisis and uncertainty that often follow diagnosis put the family at risk of exhaustion and dysfunction. Adolescents have been identified as a particularly vulnerable group of relatives. To investigate how to prevent distress in this group, we systematically reviewed research on adolescents' (11–21 years) needs for information and psycho‐social support during their mothers' breast cancer trajectory.MethodSystematic searches were conducted in five bibliometric databases. Peer‐reviewed, original research of adolescents aged 11–21 with a mother diagnosed with breast cancer was included. Two researchers conducted screening, quality assessment, and data extraction independently. Thematic synthesis was applied to the included studies.ResultsA total of 8066 studies were screened, and five quantitative and six qualitative studies were included. The results indicated that adolescents' information and psycho‐social support needs were poorly met. Many were reluctant to share feelings with family and peers and experienced abandonment during the crisis. Adolescents who were not well informed experienced distress. Poor family functioning increased the level of adolescents' distress.ConclusionsDespite limitations regarding heterogeneity among the studies, eligibility criteria, and quality assessment, this review provides clear clinical implications. Encounter groups may support adolescents during their mother's breast cancer trajectory. Furthermore, healthcare professionals could provide more indirect support to adolescents by providing support and clearer guidelines to parents. Finally, adolescents from poor‐functioning families need extra attention.