Although most research on medical error has been conducted on adult inpatient units, the few studies conducted in pediatric settings suggest that errors occur more frequently in neonatal intensive care units (NICUs) than in other inpatient units. The effects of fatigue, due to long work hours, working at night, and insufficient sleep, are often underestimated. This article reviews basic information about fatigue and sleep and includes examples drawn from data provided by 6 NICU nurses who participated in a recent study to highlight the relationship between fatigue and error. These case studies reinforce the concept that NICU nurses need to be alert enough to provide safe care for their patients, as well as alert enough to detect and correct the errors made by others. Employing good sleep habits, minimizing shift rotations and excessive work hours, and using strategic naps can reduce the adverse effects of fatigue that could potentially put patients, especially the most vulnerable ones, at risk.