Epidemiological studies have consistently reported a significant association between poverty and the prevalence of intellectual disabilities. The available evidence suggests that this association reflects two distinct processes. First, poverty causes intellectual disabilities, an effect mediated through the association between poverty and exposure to a range of environmental and psychosocial hazards. Second, families supporting a child with intellectual disabilities and adults with intellectual disabilities are at increased risk of experiencing poverty due to the financial and social impact of caring and the exclusion of people with intellectual disabilities from the workforce. It is likely that the association between poverty and intellectual disabilities accounts in part for the health and social inequalities experienced by people with intellectual disabilities and their families. Implications for policy and practice are discussed in relation to the funding of services for people with intellectual disabilities and preventative approaches to addressing the health and social inequalities experienced by people with intellectual disabilities and their families.