Grateful caregivers report lower levels of psychological distress. Social support, engendered by gratitude and buffering against stress, might mediate this effect. Here we explored whether the protective psychological effect of dispositional gratitude might be mediated by increased social support. A sample of 126 caregivers of autistic children completed questionnaires assessing dispositional gratitude, social support and psychological distress. Gratitude inversely predicted psychological distress, as did social support after adjusting for gratitude. Gratitude positively predicted social support. Gratitude no longer predicted psychological distress after adjusting for social support. Indirect effects analysis revealed the gratitude-distress relationship occurred indirectly via social support. Grateful caregivers reported higher levels of social support, and this predicted lower psychological distress. Gratitude, relatively stable as a disposition, has a state component that is sensitive to change, and healthcare professionals might do well to recommend gratitude enhancing interventions for caregivers of autistic children.