The presence of a child with an intellectual disability is often perceived as a cloud hanging over the heads of their siblings, placing them at risk of developing a variety of problems. Only recently have siblings been examined for the positive aspects of this life situation, such as the potential to experience psychological growth. Adopting J. A. Schaffer and G. H. Moos' (1992) theoretical framework, this study investigated the contribution of perceived stress, self-differentiation, and parental preference to the personal, social, and spiritual growth of siblings. Participants comprised 101 siblings of children with intellectual disabilities and 89 siblings of children with typical development (age range = 13–19 years). Results indicated that siblings of children with intellectual disabilities evidence higher levels of growth, with self-differentiation and perceived maternal preference acting as the main contributors to this growth.