The symptoms of sleepiness and fatigue are frequently encountered when caring for adolescents. Up to 40% of healthy teens experience regular sleepiness, defined as an increased tendency to fall asleep. Fatigue is the perception of low energy following normal activity and is reported by up to 30% of well teens. Chronic fatigue syndrome is an unusual syndrome with severe fatigue accompanied by other physical and neurological symptoms. A thorough assessment is required for all teens with sleepiness and fatigue; however, a treatable underlying medical condition is rarely found. Most fatigue and sleepiness in teens is attributable to lifestyle issues, notably too little time spent sleeping. Physicians are in a position to screen for, assess and manage these common conditions in teens.