Adolescent athletes frequently complain of fatigue. Acute fatigue after intense training is physiological and necessary in order to develop capacity and increase performance. However, healthcare practitioners must question persistant fatigue, which causes are multiple, sometimes clear, though mostly multifactorial. A comprehensive and holistic approach is especially required in adolescents, with a complete somatic, psychosocial and athletic history. The role of healthcare professionals is to quickly identify specific signs and complex diagnoses, which can lead to physical and psychological consequences in the long term (overtraining, burnout, abuse, eating disorders). Finally, in a time where overweight and inactivity is rampant in the youth, we must imperatively avoid adolescents dropping out of sports and activity.