The present work has been conducted through a project for biological control of olive pests in Aljouf region, Saudi Arabia Kingdom. (Steinernema spp., SAK1 isolate), (Ord. Rhabditida: Fam. Steinernematidae) and (Heterorhabditis spp., SAK2 and SAK3 isolates), (Ord. Rhabditida: Fam. Heterorhabditidae) were applied in soil around trunks of olive trees. Successive soil samples were tested for persistence and their virulence to larvae and pupae of Zeuzera pyrina L; where it is attacking olive trees and strongly considered one of the most dangerous pests. Heterorhabditis spp., SAK2 and SAK3 isolates achieved 100 % mortality to larvae and pupae of Z. pyrina at the second day, where mortality gradually decreased to 22.2 and 11.1 % after 16 days for both larvae and pupae, respectively. Steinernema spp., SAK1 isolate was less virulent, it caused 88.9 and 50.5 % mortality after two days and no mortality achieved after 16 days for both larvae and pupae of Z. pyrina, respectively. After two and four days, mortality due to the fungus is 66.7 and 44.4 %, respectively, where no mortality achieved after 8 and 16 days for both larvae and pupae of Z. pyrina, respectively. On the other hand, applying nematodes either via spraying or injection in olive branches infested with Zeuzera pyrina larvae and /or pupae caused 100% control to the insect stages inside the branches within seven days.