This experiment was carried out at the experimental farm, Faculty of Agriculture, Tanta University, during 2014 and 2015 seasons, to study the population density of onion thrips, Thrips tabaci Lind.(Thysanoptera: Thripidae) under onion field conditions. In the middel of February the population density exceeded 10 alive thrips per plant which the time of control. Population peak reached during 2^nd week of April 2014. Two entomopathogenic fungi Beauveria bassiana (Bals.) Vuill. and Metarhizium anisopliae (Metsch.) (Deuteromycotina: Hyphomycetes) isolates were treated on T. tabaci in labortatory conditions with concentrations of 10⁴, 10⁵, 10⁶, 10⁷ and 10⁸ conidia/ml. Therefore the LC₅₀ values were 0.9 x 10⁵and 2.9 x 10⁶conidia/ml. for B. bassiana and M. anisopliae isolates, respectively. Accordingly the two isolates were sprayed in the middel of february in the onion field to control T. tabaci with concentrations of  0.9 x 10⁶ and 2.9 x 10⁷ conidia/ml for  B. bassiana and M. anisopliae  isolates, respectively and compare with Actellic 50% as a recommended pesticide with 500 ml/Fadan. The reduction in insect numbers were 74, 62.87 and 87.08 % for B. Bassiana, M. anisopliae  isolates and Actellic 50%, respectively. This result revealed that the two isolates may be effective against T. tabaci in field conditions especially B. bassiana isolate.