Anagrus nilaparvatae is one of major parasitoids for Nilaparvata lugens eggs. Deltamethrin is a pyrethroid insecticide that is still used by rice farmers. This research aimed to investigate the effects of deltamethrin on the longevity, development time, emergence rate of progeny, actual and potential fecundicity of A. nilaparvatae. The insecticide was applied to the parasitoid adults at sublethal concentrations using the contact method in a test tube. The tested concentration was 0, 023 ppm (LC10) and 2, 235 ppm (LC40); and the control was treated with acetone. Each parasitoid surviving from deltamethrin treatment was exposed into N. lugens eggs in the rice seedlings for 24 hours. The seedling was then removed and substituted with new seedling until the parasitoid died. Each treatment was repeated 10 times. The application of deltametrin at sublethal concentrations decreased the longevity of adults, increased the development time of progeny, a decreased the actual and potential fecundicity, but no effect on the emergence rate. These findings suggest that the application of deltametrin to rice plants could reduce the potenty of A. nilaparvatae as a biological control agent of