Fetus-in-fetu (FIF) is a rare entity in which malformed parasitic twin grows inside the body of its twin. It is most commonly presented with mass in the abdomen. We present a case of a 15-year-old boy who presented with abdominal mass since infancy. Radiological investigations are suggestive of FIF. Intraoperatively, malformed fetus in a sac was found and excised. Postoperatively the patient recovers well and was put on follow-up.