Abstract: Three species of entomopathogenic fungi, Cladosporium uredinicola, C. cladosporioides and C. chlorocephalum were found attacking whiteflies (Bemisia spp.) in Mansoura region, Dakahlia Governorate, Egypt. Their prevalence on Bemisia infesting seven plant hosts varied from 10.0 to 28.0% according to the plant host. The morphology of these three fungi and their infection symptoms is discussed. Attempts were made to initiate artificial infections in different stages of a laboratory culture of Bemisia spp. Results indicated that eggs were infected at a lower percentage (14 to 28%), whereas the hatching rate of eggs recorded a higher percentage (56%). Pathogenicity effect on nymphs and adults were very high (88%) and varied according to the spore concentrations and periods after infection. Laboratory studies revealed that C. uredinicola gave the highest infection percentages, followed by C. cladosporioides and C. chlorocephalum. Light regime studies showed that the three species of the fungus were more aggressive on Bemisia under a diurnal light regime than under continuous darkness.