A 13-year-old girl developed suppurative rhinitis responsible for necrosis of the nasal septum. Six months later, she started experiencing arthritis in the interphalangeal joints of her right foot, then severe pneumonia with multiple nodules, She was admitted after failing several courses of antibiotics. Her laboratory tests showed marked inflammation, Wegener's granulomatosis was considered. Tests for antineutrophil cytoplasmic antibody (ANCA) were negative on two occasions. Diffuse nodular densities were seen on computed tomography scans of the chest, A surgical biopsy of Fowler's segment was performed under thoracoscopy. The histological diagnosis was Wegener's granulomatosis, Cyclophosphamide and a glucocorticoid were given for two years. At last follow-up, the outcome was favorable, the only residual abnormality being the nasal septum necrosis, Pediatric Wegener's granulomatosis is rare and difficult to diagnose. Histology of a pulmonary biopsy specimen is key to the diagnosis in patients with negative tests for ANCA. Pulmonary biopsy should be considered in patients with suggestive pulmonary, articular, and ENT symptoms but negative tests for ANCA. It is essential to make the correct diagnosis because appropriate therapy, despite the risks it entails, improves the prognosis of this disease whose natural course is frequently fatal.