Sleep disturbances and fatigue are significant problems for critically ill patients. Existing sleep disorders, underlying medical/surgical conditions, environmental factors, stress, medications, and other treatments all contribute to a patient's inability to sleep. Sleep disturbance and debilitating fatigue that originate during acute illness may continue months after discharge from intensive care units (ICUs). If these issues are unrecognized, lack of treatment may contribute to chronic sleep problems, impaired quality of life, and incomplete rehabilitation. A multidisciplinary approach that incorporates assessment of sleep disturbances and fatigue, environmental controls, appropriate pharmacologic management, and educational and behavioral interventions is necessary to reduce the impact of sleep disturbances and fatigue in ICU patients. Nurses are well positioned to identify issues in their own units that prevent effective patient sleep. This article will discuss the literature related to the occurrence, etiology, and risk factors of sleep disturbance and fatigue and describe assessment and management options in critically ill adults.