Nymphal developmental periods and mortality of Bemisia tabaci when exposed to two parasitoids Encarsia bimaculata and Eretmocerus sp. nr. furuhashii at different nymphal stages were studied in the laboratory. Developmental periods of various nymphal instars were significantly delayed among instars when parasitized by E. bimaculata and Eretmocerus sp. nr. furuhashii. Developmental periods of 1st–4th nymphal instars when originally parasitized by E. bimaculata were 20.13, 19.19, 18.65 and 17.93 days, respectively. Developmental periods were protracted when instars were parasitized by Er. sp. nr. furushashii with values of 23.16, 21.37, 20.76 and 20.31 days. However, averaged developmental periods of B. tabaci immatures without parasitism were 14.10 days. Mortalities of B. tabaci immatures were significantly different among instars when parasitized by E. bimaculata or Er. sp. nr. furuhashii. Mortality was highest at the 3rd instar and lowest at the 1st instar when parasitized by E. bimaculata, whereas when parasitized by Er. sp. nr. furuhashii, the highest mortality was found at the 3rd instar and the lowest was at the 4th instar. Mortality of B. tabaci caused by parasitoids host feeding was higher on 1st and the 4th nymphal stages than on 2nd and the 3rd stages, regardless of the species of wasps. These results indicated that deleterious effects of parasitism on whitefly development occurred on the instar that followed the instar at which parasitism has occurred; parasitism and host feeding by the aphelinid wasps are important factors that significantly influence whitefly mortality.