Fasciola hepatica, also known as the common liver fluke, is a trematod with a leaf-like and flattened body. The definitive hosts are herbivorous animals such as cattle, sheep, and goats, and it mostly causes disease in animals. Human is an incidental host. The metacercarial forms are transmitted by ingestion of aquatic plants (watercress) in contact with contaminated water. They reach the liver through the intestine, transform into adult form, and following their settlement on the bile ducts start to produce eggs. Serological methods facilitate diagnosis if eggs cannot be seen in feces. In endemic regions, fascioliasis is among the causes of fever of unknown origin (FUO). In this report, we present six adult cases who applied to the Infectious Diseases and Clinical Microbiology Outpatient Clinic with a clinical picture of FUO, and were serologically diagnosed as fascioliasis.