The present study examined the moderating role of social support and challenging behaviour on the stress–physical health relationship in parents caring for children with intellectual disabilities. Parents of children with intellectual disabilities (n = 70) reported more physical health problems compared to control parents (n = 45) and were more likely to visit their general practitioner. Furthermore, challenging behaviours, but not social support, moderated this association: parents of children with intellectual disabilities reported poorer physical health when both challenging behaviours and stress were perceived to be high. These findings suggest that interventions need to be directed towards ameliorating the impact of challenging behaviours.