To examine cortisol diurnal rhythms over the transition from the critical care setting to home for fathers and mothers of very low-birth-weight infants, including how cortisol is associated with psychosocial stress and parenting sense of competence. This cohort study in a level III neonatal intensive care unit and the general community had 86 parents complete salivary collection and self-reported psychosocial measures. Salivary samples were collected 3 times a day on the day before discharge, and on 3 subsequent days at home. Self-report measures included the Perceived Stress Scale and the Parenting Sense of Competence Scale, which measure parenting satisfaction. Fathers showed increased physiologic stress over the transition home, reflected by flattening of slopes, lower wakeup, and higher bedtime cortisol. Mothers reporting increases in perceived stress over the transition home had higher bedtime cortisol, suggesting a link between higher perceived stress and higher physiologic stress. Results were significant after controlling for breastfeeding, insurance status, and gestational age. This study examined a physiologic marker of stress in parents with very low-birth-weight infants, finding sex disparities in diurnal cortisol patterns during the transition from neonatal intensive care unit to the community. Fathers may be especially susceptible to stressors during this transition.