An adult male Malagasy giant jumping rat (Hypogeomys antimena) kept at Zoo Duisburg was presented for clinical examination because of a distended abdomen and a history of lethargy and weakness. General examination findings consisted of an enlarged soft and fluctuating abdomen, suggestive of ascites. Digital radiography revealed multiple cloud-like radiopaque lesions in the cranial abdominal area, as well as an overall decrease in visibility of detail of the abdominal organs. Ultrasound examination showed circumscribed hypo- to anechogenic areas in the liver, measuring from 1 to 3 cm in diameter, some containing irregular, convoluted structures. Exploratory laparotomy confirmed the presence of a large amount of clear, pale-yellow fluid in the peritoneal cavity, as well as multiple cystic lesions in the liver and in the greater omentum. Extirpated cysts placed in sterile saline solution or fixed in formalin were sent to the Institut für Parasitologie der Tierärztlichen Hochschule, Hannover, Germany, and were identified as larval stages of the cestode Taenia taeniaeformis. Unfortunately, the rat died a few hours after surgery. To the authors' knowledge, this is the first report of infection with strobilocerci of T. taeniaeformis in a Malagasy giant jumping rat.