This study examined who provides informal (or unpaid) supports to people with intellectual and developmental disabilities (IDD). Participants included 657 adult siblings of people with disabilities who responded to a national survey about informal supports in the areas of recreation, employment, and housing. Results indicated that most people with IDD received informal supports, with parents and sibling respondents most often providing those supports. Support was most commonly received in recreation, as opposed to housing or employment. Asked to list nonfamily informal supporters, respondents often mentioned paid staff and disability organizations. Correlates of total numbers of informal supporters included the individual with disability's functioning level and parents' ability to care for their offspring with disabilities.