The invasive fall armyworm S. frugiperda is considered nowadays the most important dangerous insect pest on the main crops especially in Egypt as it caused many losses to the Egyptian felid crops, this pest needs more alternative control methods to avoid chemical control harms, in this study, we have to estimate the virulence of two entomopathogenic nematodes on larval and pupal stages of S. frugiperda under laboratory conditions. Results indicated that mortality percentages of S. frugiperda were very satisfied with using the two entomopathogenic nematodes Steinernema carpocapsae and Heterorhabditis bacteriophora in controlling FAW larvae and pupae. As S. carpocapsae and H. bacteriophora caused high mortality percentages against the 4 larval instars of FAW, results indicate that mortality percentages reached 100% after (48-120 h) post-treatment with five concentrations of S. carpocapsae (500, 1000, 1500, 2000 and 2500 IJs) against small larval instars (3^rd and 4^th) and after (72-120 h) against older instars (5^th and 6^th) exposed to the same five concentrations. Also, results indicated that S. carpocapsae caused faster mortality than H. bacteriophora under laboratory conditions. After calculation of LC₅₀ of the two entomopathogenic nematodes against FAW  larval instars; 3^rd, 4^th, 5^th and 6^th after 72 h, LC₅₀ were; 454.183, 546.029, 600.777 and 908.079 for S. carpocapsae against the 4 larval instars, respectively, and 474.456, 552.126, 753.022 and 976.908 for the H. bacteriophora against the same four instars, this results cleared that the statistical analysis showed that there were slight or non-significant differences between the efficiency of the two EPNs in combating the fall armyworm larvae under laboratory conditions. Also, both EPNs were highly efficient in combating FAW pupae under laboratory conditions.