In this study, the antifungal activity of some antioxidants against Botrytis allii causing neck rot disease of onion and their efficacy on the disease incidence under greenhouse and field conditions and bulb weight during storage were investigated. In vitro, all evaluated antioxidants significantly reduced the mycelial linear growth and biomass at all tested concentrations. Salicylic acid at 20 mM caused the highest inhibitory effect, where it caused the highest reduction of the mycelial linear growth, and biomass reached 1.07 cm and 0.046 mg. In contrast, humic acid at 20 mM caused the lowest inhibitory effect. In the greenhouse and field trials, the antioxidants significantly varied in their effectiveness on the incidence of onion neck rot disease. The efficiency increased by increasing the concentration of each tested antioxidant. Salicylic acid at 20 mM was the most effective one and caused a high reduction in disease index (DI) and disease severity, followed by pyrogallol acid, while humic acid was the lowest effective one. During storage, the antioxidants at all concentrations tested significantly varied in their effectiveness on the incidence of neck rot disease and reduction in bulb weight of onion. The efficiency also increased by increasing the concentration of each tested antioxidant. Salicylic acid at 20 Mm caused the highest efficiency, where it caused the lowest DI and bulb weight reduction to reach 28.11 and 14.75%, respectively, compared with 77.81 and 53.63% of the control. In conclusion, this study suggests that applying antioxidants such as salicylic and pyrogallol acids could be effectively used to control neck rot disease of onion as alternaive approach instead of fungicieds.