Streptococcal toxic shock syndrome (TSS) with the initial manifestation of peritonitis is rare. We report the case of a 5-year-old girl who presented with peritonitis and shock. Emergency laparotomy was performed but no perforated visceral organ was found. Acute respiratory distress syndrome, impaired renal function, and coagulopathy developed later. Group A beta-hemolytic Streptococcus (GAS) was isolated from the pleural effusion and the diagnosis of streptococcal TSS was made. This association highlights the need for thorough examination and close observation in the management of childhood peritonitis.