Onion white rot is one of the most destructive diseases threat onion production in Egypt. The present study assessed the effect of Purpureocillium lilacinum culture filtrates in vitro and in vivo conditions on Stromatinia cepivora at 75% concentration. Bioagent culture filtrates inhibited the mycelial growth, sclerotial formation and myceliogenic germination of S. cepivora by 82.59, 100 and 93.33%, respectively. The culture filtrates at 75% increased cell membrane permeability of S. cepivora compared to the control. The in vitro analysis revealed that 92.5% of the sclerotia were lost its activity in the soil when treated with filtrates and significantly decreased the disease incidence and severity by 95.10 and 98.30%, respectively under greenhouse conditions. However, soil previously infested with S. cepivora sclerotia and handled continuously with bioagent culture filtrate for 6 months before onion cultivation undoubtedly decreased the disease incidence and severity. During 6 months after field culture filtrates treatment, more than 80 and 60% of the sclerotia failed to emergence in trial I and II plots experiment, respectively. After one-year culture filtrate treatment in consecutive onion field crop cultivation, filtrates were more efficient than control in decreasing white rot incidence attendant with low inoculum density trial field (77.67 sclerotia/kg of soil). Consequently, a decrease in white rot incidence resulting promotion to vegetative parameters of culture filtrate treated onion plants in pots and increase growth and bulb yield productivity in field. Decreasing disease incidence and severity was associated with increase activities of antioxidant enzymes polyphenol oxidase, peroxidase and chitinase by application of culture filtrates.