Eupatorium adenophorum is considered to be a serious weed in agriculture, especially in rangelands where it often replaces either the more-desirable vegetation or native species, but also in forests. Grazing animals get accidentally exposed to the plant under scarcity conditions. A considerable variation between the animal species exists in terms of susceptibility to toxicity due to E. adenophorum. It is generally unpalatable to grazing animals, but goats graze on this plant infrequently. It is fatally toxic to horses and causes the “blowing disease” in Hawaii and “Numinbah disease” or “Tollebudgera horse disease” in Australia. Toxicopathological studies were taken up in Swiss albino mice, as a model and the effects of the plant extract on hematological, biochemical, gross pathological and histopathological parameters were recorded. The plant extract was found to be highly hepatotoxic in mice as evidenced by the changes in blood-biochemical, liver enzyme activities, gross and histopathology of liver. The results of the study suggest that the consumption of the extract of E. adenophorum as medicinal purposes without proper dosing may produce hepatotoxicity in humans.