BACKGROUND: To compare the skin and breast/cervical cancer prevention/screening practices of adult siblings of childhood cancer survivors with controls and to identify modifying factors for these practices. METHODS: Cross-sectional, self-report data from 2,588 adult siblings of 5+ year survivors of childhood cancer were analyzed to assess cancer prevention/screening practices. Two age, sex, and race/ethnicity-matched samples (N = 5,915 and N = 37,789) of the Behavioral Risk Factor Surveillance System participants served as the comparison populations. Sociodemographic and cancer-related data were explored as modifying factors for sibling cancer prevention/screening practices through multivariable logistic regression. RESULTS: Compared with controls, siblings were more likely to practice skin cancer prevention behaviors: use of protective clothing [OR, 2.85; 95% confidence interval (CI), 2.39-3.39], use of shade (OR, 2.11; 95% CI, 1.88-2.36), use of sunscreen (OR, 1.27; 95% CI, 1.14-1.40), and wearing a hat (OR, 1.77; 95% CI, 1.58-1.98). No differences were noted for breast/cervical cancer screening including mammography and Pap testing. Having less than a high school education and lack of health insurance were associated with diminished cancer prevention/screening behaviors. Survivor diagnosis, treatment intensity, adverse health, chronic health conditions, and second cancers were not associated with sibling cancer prevention/screening behaviors. CONCLUSIONS: Siblings of cancer survivors report greater skin cancer prevention practices when compared with controls; however, no differences were noted for breast/cervical cancer screening practices. Access to care and lack of education may be associated with decreased cancer prevention/screening behaviors. Interventions are needed to address these barriers. IMPACT: Research should be directed at understanding the impact of the cancer experience on sibling health behaviors.