The ar cle presents the results of studies of the effect of fenbenzyl and fenbendazole on the an oxidant status in dogs under the experimental infec on with a causa ve agent of toxocariasis. Experiments were performed on 18 dogs, two and four months old. Three groups of six animals in each were formed: control and two experimental. Puppies in all groups were experimentally infected with causa ve agent of toxocariasis at a dose of 5.000 embryonated Toxocara canis eggs per kg of body weight. The control group of dogs was as untreated control. Puppies of the first experimental group were fed with the drug fenbendazole at a dose of 150 mg per 3 kg of body weight once a day for three days in a single dose. Puppies of the second experimental group were fed with the drug fenbenzyl at a dose of 350 mg per 3 kg of body weight once a day for three days. While studying the ac vity of the enzyma c part of the an oxidant defense system, namely catalase, superoxide dismutase, glutathione peroxidase, glutathione reductase, as well as a non-enzyma c part: the level of reduced glutathione, an increase in the ac vity of these indicators was found in animals of experimental groups. It should be noted that the applica on of the drug fenbenzyl in infected dogs contributed to a be er normaliza on of the an oxidant system in animals than the use of the drug fenbendazole. The use of fenbenzyl in infected dogs contributed to a more likely increase in the an oxidant status in dogs of the second experimental group, as this drug includes milk thistle that exhibits an oxidant proper es due to the presence of silymarin, which restores damaged liver cells. Studies confirm the effec veness of the use of milk thistle in drug fenbenzyl in dogs with the development of toxocariasis infec on to ac vate the protec ve systems of their body.