Aim and Background: Invasive Streptococcus pyogenes infections pose a significant clinical challenge in terms of diagnostic and optimal therapeutic options. Case description: We report a case of a healthy, well vaccinated, four-year-old boy presenting with a right pneumonia complicated by a large parapneumonic effusion with negative blood culture. The patient had been treated conservatively by IV penicillin with clinical, biological and radiological improvement allowing discharge at day 21 with oral amoxicillin. At day 27, inflammatory syndrome and fever increased again and were associated with a voluminous mediastinal mass. A thoracoscopy was performed and revealed a massive S. pyogenes empyema that has required drainage. The patient recovered after 6 weeks antibiotics treatment. Conclusion: This unusual evolution of complicated S. pyogenes pneumonia demonstrated how complex clinical care might sometimes be, especially with children. Clinical significance: Indications of drainages in severe paediatric pleural effusions, including those due to S. pyogenes, vary according to guidelines and are mainly based on expert opinions. Most cases however have a favourable outcome whatever the management might be. Finally, clinical follow up is often characterised by prolonged fever which may, or not, be indicative of therapeutic failure.