Mesenchymal hamartoma of the liver (MHL) is a rare lesion occurring mainly in infants and children. It is often misdiagnosed clinically as a malignant tumor because of its rapid increase in size within a short period of time, or as a hepatic cyst or abscess because of its cystic appearance. Although a benign lesion, MHL may cause heart failure, due to arteriovenous shunts, or death if untreated, as a result of respiratory complications. A typical case of MHL was recently encountered in a 15-month-old boy. The patient presented with progressive abdominal distension; surgery revealed a large mass arising from the right lobe of the liver. The mass was predominantly solid, but collections of fluid were also present. Loose mesenchymal tissue and branched, tortuous bile ducts were the key diagnostic features. When predominantly cystic, MHL may mimic a lymphangioma both grossly and microscopically. Prudent examination of the cystic structures can establish a correct diagnosis.