Background. The article presents a study of the antioxidant defense system of the liver of rats under the influence of thiosulfonate esters: S-ethyl-4-aminobenzenethiosulfonate (ETS), S-allyl-4-aminobenzenethiosulfonate (ATS) and S-allyl-4-acetyl-aminobenzenethiosulfonate (AATS) at concentrations of 50 and 100 mg per kg of body weight. Thiosulfonate esters, which are synthetic sulfur-containing analogs of allicin, exhibit antioxidant and anti-inflammatory properties. The liver is the main organ where metabolism of xenobiotics and endogenous molecules occur to maintain metabolic homeostasis of the body, and is constantly exposed to reactive oxygen species (ROS) and subsequently to oxidative stress. Materials and Methods. The effectiveness of the antioxidant defense system in the rats’ liver was evaluated by measuring the level of oxidative stress markers (lipid peroxidation (LPO)) and the activity of the antioxidant enzymes – catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GP), glutathione reductase (GR), and the level of reduced glutathione (GSH). Results. The potential antioxidant properties of thiosulfonate esters and their dose-dependent effect in the liver were determined. In particular, under the action of thiosulfonate esters at a dose of 100 mg/kg, the content of lipid peroxidation products in the liver did not change significantly. Catalase activity and the content of reduced glutathione increased under the action of ETS dose of 100 mg/kg. Under the action of ATS and AATS doses of 100 mg/kg, the activity of GP decreased. At the same time, the effect of ETS at a dose of 50 mg/kg significantly decreased the level of lipid hydroperoxides. The effect of ATS and AATS doses of 50 mg/kg decreased TBA-reactive products. Under the action of the studied compounds in a lower dose, the activity of SOD and GP increased, and the content of reduced glutathione increased. At the same time, the decrease in the activity of GR under the action of AATS combined with an increased content of reduced glutathione is probably due to the inhibitory effect of the test substance on energy processes in the body. Conclusions. The studied thiosulfonate esters demonstrated a dose-dependent effect on the redox balance in the rats’ liver, proving to be more effective with lower doses of thiosulfonates.