Abstract: Whiteflies are one of important pests in crop production worldwide. Entomopathogenic fungus Lecanicillium spp. is a well-known biological control agent against whiteflies. Lecanicillium spp. has been reported to have high pathogenicity to larvae and adult whitefly, but there is very little information about effect to whiteflies eggs. We evaluated the effect of L. longisporum and L. muscarium against eggs of Trialeurodes vaporariorum and Bemisia tabaci. The hatching rate of T. vaporariorum eggs decreased after inoculation of Lecanicillium spp., with no significance in B. tabaci egg. Fungal invasion to egg on both whitefly species was confirmed. Egg invasion rate corresponded with reduction of hatching rate, and that the decline in the hatching rate might have been caused by the direct invasion of Lecanicillium spp. into egg. Furthermore, Lecanicillium spp. showed high mortality rate (50-90%) against hatching larvae of both whiteflies. Meanwhile, hatching rate and invasion rate of Lecanicillium spp. inoculated whiteflies egg was higher in immature yellow eggs than mature blackish eggs. This is because immature yellow eggs don’t have a hard-outer protective shell that can inhibit Lecanicillium spp. invasion. Likewise, the mature blackish egg was able to resist infection because of the outer hard shell. In conclusion, Lecanicillium spp. can infect whiteflies eggs, with a decrease in hatching rate. Therefore, there is possibility that whitefly egg might be a new target in the developmental stage which can be under microbial control.