Background: Informal caregivers provide valuable care for ill or disabled adults. Nevertheless, many caregivers experience negative consequences from caregiving such as reduced mental health. Balancing personal costs of caregiving with caregivers' desires or obligations to provide care, is necessary to promote the well-being of these individuals and their care recipients. Drawing on a self-determination theory (SDT) perspective, caregivers whose psychological needs for relatedness, autonomy, and competence are satisfied with their care recipient, and their care recipients' healthcare providers, should be more autonomously motivated to care. Greater autonomous motivation should promote better mental health. Methods: This study tested mediation models in a sample of 158 caregivers in the United States. Autonomous motivation was examined as a mediator of the (a) associations between caregivers' need satisfaction with their care recipient and caregiver burden and depressive symptoms, and (b) associations between caregivers' autonomy support received from their care recipients' healthcare providers and caregiver burden and depressive symptoms. Next, specific types of motivation that vary in their relative autonomy were examined as unique mediators. Findings: Support was found for models using autonomous motivation as the mediator. Additionally, caregivers' autonomy support and female caregivers' need satisfaction were positively associated with intrinsic motivation to care which was negatively associated with burden. Although much research suggests caregivers' outcomes stem from the care recipients' condition, such as their functional dependence on others, the present study focused on the caregivers' relationships and motivations. Conclusions: Results support an SDT perspective of caregiving.