Objectives: We examined whether providing daily support to generations above and below has a differential impact on midlife adults' diurnal cortisol. Method: Midlife adults (N = 151) from the Family Exchanges Study Wave 2 reported daily practical support, emotional support, and advice to adult children and aging parents and collected saliva samples four times a day for 4 days. Results: Midlife adults experienced steeper cortisol awakening responses and steeper declines in cortisol (favorable cortisol functioning) on days when they provided support to children. Yet, they experienced higher overall cortisol levels (unfavorable cortisol functioning) on days when they provided support to aging parents. Discussion: Providing daily support to children may be rewarding to midlife adults, but support to parents may be associated with physiological stress. Findings advance understanding of midlife adults' helping behaviors to multiple generations and carry implications for older adults' well-being by encouraging effective support strategies.