Spontaneous perforation of the extrahepatic bile duct leading to biliary peritonitis is a rare occurrence once other causes of biliary peritonitis, such as trauma, choledochal cyst, stone diseases, and distal atresia of the bile duct, are ruled out. A 7-month-old male infant was brought to the hospital in critical condition with distension of the abdomen. He had a history of vomiting and diarrhoea, low-grade fever, and refusal to feed for 2 days. Signs of peritonitis were found upon examination. Due to the poor general condition of the patient, the case was taken up for laparotomy, and a diagnosis of spontaneous extrahepatic bile duct perforation was made intra-operatively. In the present case, the cause was idiopathic. An external drain was placed near the site of the leak for 2 weeks. The patient recovered well and was discharged on post-operative day 16. Disease awareness for correct pre-operative diagnosis and interventional planning is required to reduce mortality, morbidity, and complications in spontaneous perforation of the common bile duct.