The present study aimed to evaluate the effect of three isolates of Egyptian Nuclearpolyhedrovirus geographically different, namely NPV _El-Qalioubia, NPV _Al-Fayoum and NPV _El-Beheira which isolated in Bio-insectcide Production Unit Plant Protection Research Institute, were evaluated against Spodoptera littoralis larvae under laboratory conditions. Five concentrations of Occlusion Bodies (OBs) from each of the three NPVs isolates (1×10⁶, 1×10⁷, 1×10⁸, 1×10⁹ and 1×10¹⁰ PIB/ml) were used against 2^nd insters larvae of S.  littoralis. The results showed that the percentage mortality of the larvae increased with increasing concentrations of tested pathogens. Also, the isolate NPV _Al-Fayoum was the most effective against S. littoralis larvae at different tested concentrations. In biological Studies all tested NPVs isolates decreased the mean larval duration than untreated larvae and decreased of pupation.NPV _Al-Fayoum recorded the least Pupation percentage 45.7%.  All tested NPVs isolates showed significantly shortening in the mean adult longevity for both males and females. All tested NPVs isolates significantly decreased the mean number of eggs laid and hatched /female.