Primary peritonitis, a bacterial infection within the peritoneal cavity that arises in the absence of an intraperitoneal source, is a rare entity in paediatrics. We describe the case of a previously healthy 11-year-old girl who presented with an acute abdomen and was found to have primary peritonitis due to Streptococcus pyogenes. She had an episode of pharyngitis with pharyngeal cultures positive for S. pyogenes in the month prior to presentation. We performed a review of the literature to better elucidate the risk factors, pathophysiology and presentation of peritonitis due to S. pyogenes and to draw attention to the potential association between group A streptococcal pharyngitis and peritonitis.