Choledochal cyst are rare congenital disease of the biliary tree. It presenting as cystic dilatations of the biliary tree can involve the extrahepatic biliary radicles, the intrahepatic biliary radicles or both. They are typically a surgical problem of infancy and childhood, but less than a quarter of the patients the diagnosis is delayed until adulthood as it presenting with vague and nonspecific signs and symptoms. In a case with biliary symptoms, abdominal ultrasound scan is the initial imaging modality of choice. Precise and accurate delineation of the biliary system mandates cholangiography with the advantage of non-invasive magnetic resonance cholangiopancreatography (MRCP) over endoscopic retrograde cholangiopancreatography. A case report of 11-year-old Tanzania girl with abdominal swelling and jaundice presented to a health facility for evaluation. She complained of abdominal swelling that her mother noticed when she was 3 years old, located above the umbilicus and since then it was not changed its size until 8 years later when it rapidly increased in size associated with non-specific dull pain. Abdominal computed tomography (CT) scan was done showed A well-defined hypo-attenuated non-enhancing retro-gastric cyst. Percutaneous transhepatic cholangiopancreatography (PTC) was performed due to inconclusive findings from CT-scan showed extrahepatic huge cystic dilatation, dilated central right hepatic ducts, left intrahepatic ducts failed to be visualize. Diagnosis of choledochal cyst type isovaleric acidaemia (IVA) was made. Explorative laparotomy was done, huge cystic mass occupying common bile duct was seen below the liver with distended gallbladder covered with visceral peritoneum. Second part of duodenum, pancreases and transverse colon was adhered to the inferior surface of the mass that further make difficult for cyst excision and reconstruction. Cyst was decongested and cholangioenterostomy with Roue-en-Y reconstruction was made. Cholecystectomy was done, hemostasis archived abdomen closed and patient sent to Intensive care units (ICU). Despite of advanced diagnostic modalities, delayed diagnosis of choledochal cyst can be a challenge due to its vague and nonspecific signs and symptoms. Excision of the cyst and reconstruction by hepatojejunostomy as the standard therapy could be difficult due to its biliary complications such as adhesion and infection and hence cyst-enterostomy drainage procedure can be done as option for relief of patient discomfort and prevent further complications.