Giant liver fluke (Fascioloides magna) infection is an important health problem of cervids in southeastern Europe. We measured the prevalence and intensity of infection with F. magna in a fenced area near the Danube River in the South Bačka District of Serbia. Parasitologic, pathomorphologic, and histopathologic examinations were conducted from November 2007 to February 2008, beginning with a population of 127 adult fallow deer (Dama dama). After a positive diagnosis, therapy with triclabendazole-medicated corn was applied. Deer were treated at four baiting stations, using medicated feed providing triclabendazole at an estimated dose of 10–14 mg/kg of body weight per deer. Treatment lasted for 7 d in early February 2008 and an additional 7 d 2 wk later. For the complete success of pharmacotherapy it was necessary to prevent any contact of deer with the snail intermediate host (Galba truncatula). Intervention in the habitat, removing grass and low vegetation, and draining ponds reduces the possibility of contact. Six months after the treatment, livers of hunted deer were reddish, with fibrous tracks; pigmentation and cysts in the parenchyma were surrounded by a fibrous capsule and their fecal samples contained no eggs of F. magna. Over the following years, livers of hunted deer were negative, and the last control cull in March 2015 confirmed complete absence of infection. We reconfirmed the presence of giant liver flukes in fallow deer in Serbia, apparently the result of natural spread across the Danube from Hungary and Croatia. We also report that the treatment of deer with triclabendazole-medicated corn is an effective method for administration of therapeutic doses of drug in semicaptive deer. Interventions in the environment are necessary to prevent recontact of deer with habitats used by the snail intermediate host, and enable the success of the therapy.