Sibling caregivers comprise a population of increasing significance to, intellectual/developmental disabilities (I/DD) policy and practice. As persons with I/DD and their caregiving parents age, more families are relying on adult siblings to provide care. Today, 70% of persons with I/DD live with family members; estimates indicate that up to 20% may reside with siblings. Sibling caregiving has potential to meet some of the growing social need for later life care of individuals with I/DD. However, the needs of siblings providing care are often not addressed by the service system. Inadequate knowledge about how siblings come to be caregivers and their caregiving needs hinders efforts to assist siblings who are providing care or considering whether to assume care. This study sought to discover factors associated with successful sibling caregiving outcomes and to investigate sibling caregivers’ needs for information, services, and decision-making assistance. The initial decision to assume a caregiving role was examined retrospectively and future caregiving intentions were assessed. A web-based questionnaire focusing on decision-making processes, dynamics, and satisfaction; service needs; and intent to continue caregiving in the future was completed by 1,073 adult sibling caregivers from across the United States. Results were analyzed using logistic and multiple linear regressions to test hypotheses, with interaction effects examined to identify the impact of sibling caregivers’ stage of life on caregiving decisionmaking satisfaction and future caregiving intent.