Purpose of the Study: Middle-aged adults are often called upon to support aging parents. However, providing support to an aging parent with health problems and disability may be a stressful experience. This study asked whether giving everyday support to parents in the context of health problems and disability has implications for middle-aged children's diurnal cortisol and daily mood.Design and Methods: During four consecutive days, 148 middle-aged adults (mean age = 55) reported the support they gave to their parents and provided saliva 4 times a day (wake, 30 min post-wake, lunchtime, and bedtime). Multilevel models estimated within-person differences in positive affect (PA) and negative affect (NA), cortisol awakening response and area under the curve with respect to ground (AUC-G) as a function of giving same-day and previous-day support. We examined whether these associations are exacerbated when a parent has health problems or activities of daily living (ADL) needs.Results: Middle-aged children had significantly higher next-day AUC-G on days after they gave support to parents with ADL needs. When participants gave support to parents with ADL needs, they had significantly greater same-day PA and lower next-day NA. Giving support to parents with health problems was associated with significantly higher next-day NA.Implications: Giving support to parents is an ambiguous experience with implications for biological stress and daily mood. A biopsychosocial approach reveals under what conditions giving support to parents may become detrimental to health and well-being; this knowledge is essential for the development and implementation of interventions.