Objectives: To contrast the level of anxiety and depression reported by older Australians providing assistance to someone who is ill, disabled or elderly with that of non-caregivers; and to identify secondary stressors and mediating factors which explain caregivers' poorer mental health. Method: Analysis of data from wave 2 of the PATH Through Life Study, a community survey of 2,222 adults aged 6469 years conducted in Canberra and Queanbeyan, Australia. Mental health was assessed using the Goldberg depression and anxiety scales. Analyses focused on those who identified themselves as a primary carer and/or reported providing care for more than 5 hours per week. Analyses evaluated whether the association between caregiver status and mental health was mediated by financial factors, role strain, physical health, and social support and conflict with family and friends after adjusting for demographics. Results: Caregivers reported significantly poorer mental health than non-caregivers, and also reported poorer physical health, greater financial stress, greater responsibility for household tasks, and more conflict and less social support from their family and spouse. Mediation analysis showed that the poorer mental health of caregivers reflected elevated rates of their own physical impairment, a lack of social support and greater conflict. Conclusions: The relationship between caregiving and mental health was largely explained by social support and levels of conflict within the family, which are modifiable and potentially amenable to change through policy and intervention. Research such as this can assist the development of appropriate interventions to improve the circumstances of informal caregivers in Australia.