Trialeurodes vaporariorum which belongs to the order Hemiptera and the family Aleyrodidae can lead to severe economic losses. It’s life cycle contians egg, four larval and adult stages. Fungi seem to be the only entomopathogenes that may be used to control whiteflies because thay are able to penetrate their hosts, while other pathogens need some routes to enter their host. Most fungal pathogens of whiteflies belong to the genera Aschersonia , Beauveria , Lecanicillium and Paecilomyces . The aim of this project was to investigate the singular and combined effect of the entomopathogenic fungi Beauveria bassiana and Lecanicillium muscarium and imidacloprid insecticide for control of greenhouse whitefly. Before commencing the transfer of greenhouse whitefly, each tomato leaflet was covered with a clip cage. Approximately 40 adults, randomly collected from a single population, were transferred into each cage. They were then allowed to lay eggs on the leaflet for 72h at 24±1?C, 70±10 R.H under 16:8 (L:D) phoroperiod 11 days prior starting of experiment. This time interval resulted in first and second instar nymphs to appear, and 20 days after, all nymphs in third and fourth instars appeared at the time of fungal inoculation. The fungi were cultured in Petri dishes containing PDA in the incubator. In fungal bioassay, conidial suspension was sprayed on detached leaves. conidia suspensions containing 10 3 -10 6 conidia ml -1 was applied to the underside of each leaflet using a Potter spray tower with fine droplet spray nozzle in a randomized complete block design. A control leaflet was treated with 2 ml of sterile distilled water containing 0.01%Tween 80. The dishes were incubated in an incubator at 24±1?C ,70±10 R.H set under 16h light and 8h dark. Insects that were either covered by dense hyphal growth or whose colour changed from traarent greenish to opaque white or light yellow were considered dead similarly. The bioassay of imidacloprid was performed the same way as bioassay of entomopathogenic fungi. The mean viability of the spores of the straines applied to all the developmental stages in the parental generation was 95.5%. The results showed that imidacloprid is not compatible with L. muscarium and it caused complete inhibition in fungal vegetative growth in 2 MC (Mean Concentration) but average daily growth increase of B. bassiana was not significantly different in comparison with the control. Likewise, germination of conidia at 2 MC treatment was not affected with imidacloprid while in L. muscarium , the rate of germinated conidia was reduced