This study aimed to investigate the insecticidal activity of two Nano materials (Nano Silver and Nano Silica) against the Cotton Leaf Worm, Spodopetra littoralis in Agriculture research farm, during season 2020/2021. The two Nano materials were characterized by SEM and TEM. Four concentrations were applied for each Nano material (4000, 3500, 3000 and 2500 ppm). The tested two Nano materials significantly reduced the pest population compared to control. The result showed that nano silver material had a toxic effect against 2nd instar larvae of cotton leaf worm specially at 4000 ppm reached to 85.00 % after 12 days of treatment to 6.6 % in un treated also decreased adult emergency to 10.00% compared with 93.43 % in un treated, this mean it had broken life cycle of leaf worm nano Silica on both second & fourth instar larvae recorded mortality 80.00, 77.66, 75.00 and 73.33% in 2nd instar larvae, while recorded 73.33, 68.33, 66.66 and 35.00% in 4th instar larvae compared with control 6.66 & 5.00 %. In pupation % we find a reverse relationship between it and conc. All tested materials had initial & latent toxic effect and developmental effect, this effect increased as both period after treatment and concentration increased. Nano silver showed the highest effect followed by silica, while silver showed the highest antifeedant effect followed by silica. Although silver showed the highest effect, silica is suitable for application for economic consideration and for its local availability.