Sulfur is considered an essential macronutrient during plant growth and is found to play critical roles in xenobiotics detoxifying processes in plants. In the present study, the effects of exogenous sulfur treatment as additional fertilization on detoxifying enzymes activities and plant health indicators were investigated in eggplant (Solanum melongena) seedlings exposed to excessive doses of thiacloprid. Eggplant seedlings (cultivar Hansel F1) were irrigated with ammonium sulfate (140 mg L^-1) at 14 days after sowing in combination with the spraying of a 4-fold recommended dose of thiacloprid. In another treatment, seedlings received ammonium sulfate (70 mg L^-1) as a minimum sulfur need in their growth in combination with a mentioned dose of thiacloprid. After 14 days of treatment, leaves were collected to determine their physiological parameters. Based on results, plant health indicators including malondialdehyde, hydrogen peroxide, and electrolyte leakage index were significantly lower in treatments that were received additional amounts of sulfur than other ones. While, the activities of glutathione S-transferase, glutathione reductase, glutathione peroxidase, thioredoxin reductase, and cytochrome P450 monooxygenase were higher in them. Our findings suggest that the sulfur can decrease membrane permeability and increase cell viability as well as magnify their detoxification capacity which consequently leads to the reduction of oxidative damage in plants. It can be concluded that the sulfur supply in eggplant farms that thiacloprid is intensively used against sap feeder insects should be considered because it can lead to reducing potential risk to the environment by decreasing pesticide damage to host plants as non-target organisms