Background: Providing long-term care to an adult relative with intellectual disability can impact negatively on caregivers' health and well-being. Methods: Data were collected via online and postal questionnaires on 110 family carers' physical and psychological health, family stress and perceived positive gains from caring. Psychological adaptation and carers' satisfaction with available support were also examined. Results: Study participants reported more health problems than general populations. Higher support needs of care recipients were associated with increased family stress. Carers being female were associated with lower family stress. Older age and better socio-economic position were associated with better psychological outcomes. Other associations were consistent with psychological adaption and perceived helpfulness of support buffering negative outcomes and facilitating positive gains from caring. Conclusions: Family carers of adults with intellectual disability appear to experience poorer health outcome than population norms. Adaption to the caregiving role may buffer negative outcomes. Further large scale, population-based, longitudinal research is needed.