This descriptive study was performed to identify the relationships among alienation, general social support, and nurses' support for the siblings of children with cancer. The participants were 84 siblings of children with cancer. Alienation was measured by the revised version of Dean's Alienation Scale, and general social support was quantified by the revised version of Dubow and Ullman's Social Support Appraisal Scale. For nurses' support, Murray's Nurse-Sibling Social Support Questionnaire was used. Data were collected from July 2011 to December 2011. The participants' alienation was not particularly high (mean = 42.24 ± 12.72), but psychosocial vulnerability was identified from their answers to open-ended questions. The participants' perceived alienation showed a negative correlation with general social support, but no relationship with nurses' support. Although direct relationships between nurses' support and the siblings' alienation were not found in this study, the siblings perceived that the support of nurses was moderately helpful. Nurses can help siblings by providing support.