Informal caregivers experience a great deal of stress due to care-related duties and responsibilities. Caregiving stress has the ability to impact caregivers' physical health, but has been largely understudied in caregivers of children with a chronic illness. In this study, we examine the associations of stress to both caregiver self-rated health and biomarkers of the hypothalamic-pituitary-adrenal (HPA) axis and immune systems (arginine vasopressin, c-reactive protein, tumor necrosis factor alpha). We also examine whether coping style (proactive, avoidant, support coping) buffers the links of stress to health across two different stressor contexts: caregiving for a child with a rare or undiagnosed disease ( n = 101) and caregiving for a typically developing child ( n = 69). Results indicated perceived stress was linked to worse self-rated health, however, stress was only linked to biological markers of health for caregivers of typically developing children. Results also suggest that coping style may moderate some of the links of stress to health, as proactive coping was linked to lower arginine vasopressin. However, models also suggested the role of coping style may differ based on caregiving context, as support coping was linked to better health only for caregivers of typically developing children, and more proactive coping overall was observed in the rare disease context. Future research should continue to examine how stress and coping interact within different caregiving contexts to protect caregiver health and well-being.