Objective: The purpose of this study was to explore whether childhood family environments moderated the relation between daily stress and daily biological outcomes (sleep, cortisol output) in healthy young adults. Design: There were 87 participants, ages 19 to 25 who provided information on characteristics of their childhood family environment (conflict, parental warmth). Main Outcome Measures: For 1 week they completed a daily stress checklist via electronic diary, provided salivary cortisol samples 4 times a day, and wore an Actiwatch to measure sleep (minutes, efficiency). Data was analyzed using hierarchical linear modeling. Results: Family risk significantly moderated the relation between daily number of stressors and sleep minutes (b = -12.10 p = .02), such that the more difficult one's childhood environment, the less sleep individuals got on days in which they experienced a greater number of stressors. Parental warmth moderated the relation between stress severity and cortisol output (b = -0.19, p = .04), such that the less parental warmth individuals received during childhood, the more cortisol they secreted on days that they experienced more severe stress. Conclusions: The childhood psychosocial environment may have long-term effects on biological responses to daily stress, creating vulnerability to disease in individuals from difficult childhoods.