Background: To examine the relationship between social support and depressive symptoms of Chinese family caregivers of older people with disabilities, and to evaluate the role of caregiver burden as a potential mediator of that relationship.; Methods: A survey questionnaire was completed face-to-face by 567 primary family caregivers of older people with disabilities in four provinces in China. Covariates that may affect depressive symptoms, such as the characteristics of disabled people (socio-economic factors, functional and cognitive capacity) and caregivers (caregiver duration and self-rated health of caregivers) were collected. Social support was measured by the Multidimensional Scale of Perceived Social Support (MSPSS); depressive symptoms were assessed by the shortened 10 item version of Center for Epidemiological Studies Depression scale (CES-D); and the caregiver burden was assessed by the Zarit Burden Interview (ZBI).; Results: The prevalence of depressive symptoms among caregivers was 37.7%. Higher levels of social support was negatively associated with lower depressive symptoms. This relationship was partially mediated by the caregiver burden, where higher levels of the caregiver burden were negatively associated with depressive symptoms. Furthermore, caregivers who were women, spent extended time in caregiving and were in poor health, reported significantly higher depressive symptoms.; Conclusions: Our results indicated that social support was negatively associated with depressive symptoms in family caregivers and in the caregiver burden. The caregiver burden partially mediated the social support-depressive symptoms association. Interventions for family caregivers should include increasing social support, health monitoring and structured interventions to reduce the caregiver burden and attenuate family caregivers' depressive symptoms.