We describe the rare case of a 12-year-old boy complaining of repetitive severe pain in the left thigh, during physical activity related to a femoral neck stress fracture. Even though stress fractures are common in the adult athletic population, they occur rarely in children, with the epiphyseal growth plates still open. Diagnosis is delayed as only unspecific changes are found when conventional radiography is performed. For adequate treatment, early diagnosis by MRT or bone scintigraphy is essential. Conservative treatment will be effective through prevention of overuse.