Hydatid cyst disease is a zoonosis caused by the parasite Echinococcus. It may infest any organ of the body, but it most frequently involves the liver, lungs, and nervous system. Portal vein involvement by hydatid cyst disease is extremely rare with only five cases published in the English literature to our knowledge. We present the ultrasonography (US) and computed tomography (CT) findings of a 77-year-old male with hydatid disease of the liver with portal vein invasion mimicking portal vein thrombosis. Colour Doppler US confirmed the lack of blood flow within the portal vein and stigmata of cavernomatosis. CT clearly demonstrated a communication between the multiloculated lesion and the portal vein and the multiple daughter vesicles obstructing the portal vein. The consideration of this complication will make it possible to distinguish this entity from portal vein thrombosis and, thus, the management of the patients with hydatid cyst disease particulary in endemic regions.