Background When compared with their nonintellectually disabled peers, people with intellectual disabilities (IDs) have poorer health and are more likely to be exposed to poverty during childhood. Given that exposure to child poverty has been linked to poorer health outcomes, we attempted to estimate the extent to which the health inequalities faced by children and adolescents with IDs may be accounted for by their more disadvantaged socio-economic position. Methods Secondary analysis of data on a nationally representative sample of 12 160 British children aged under 17 years extracted from the Department of Work and Pensions’ Families and Children Study. Results After controlling for age and sex, children with IDs were significantly more likely (corrected odds ratio = 2.49) to be reported to have less than good health than their nonintellectually disabled peers. However, 31% of the elevated risk for poorer health was accounted for by between-group differences in socio-economic position and social capital. Conclusions A socially and statistically significant proportion of the increased risk of poorer health among children and adolescents with IDs may be attributed to their increased risk of socio-economic disadvantage.