Although many siblings show resilience in the face of childhood cancer, others report clinical levels of distress during and after cancer treatment. Psychosocial care is recommended for siblings, but systematic screening to identify siblings currently experiencing or at-risk for psychosocial difficulties is not routine. As part of a program of research to develop feasible procedures for sibling screening, the current study used qualitative methods to gather the perspectives of parents and siblings regarding barriers to sibling psychosocial screening, ways to mitigate those barriers, and preferred screening procedures. A purposive sample of families of children with cancer (n = 29 parents, n = 17 siblings ages 8–17) participated in semistructured qualitative interviews. Barriers to and preferences for sibling screening (e.g., timing, location, modality) were probed. Applied thematic analysis was used to distill findings. Families reported a strong need for sibling psychosocial screening but also reported barriers (i.e., family disruptions and separations, parental stress, and hesitancy to disclose emotional difficulties by both siblings and parents). Recommendations for addressing these barriers were provided. Sibling screening was preferred near diagnosis and every three months thereafter. Parent and sibling reports were both recommended. Preferred modalities included electronic questionnaire delivered in the hospital/clinic (parents) and clinical interview (siblings). In sum, families emphasized the importance of sibling psychosocial screening and suggested ways to achieve this. Involving families in the development of procedures to systematically screen siblings of children with cancer for psychosocial difficulties is an important step in developing feasible, effective strategies to identify siblings in need of clinical care.