Parasitism rates and parasitoid development can be influenced by the species and developmental stage of the host, both of these factors can influence parasitoid performance and fitness. In this study, parasitism rates and developmental parameters were assessed for two widely distributed and commercially available species of aphid parasitoid: Aphidius ervi (Hymenoptera: Braconidae) and Aphelinus abdominalis (Hymenoptera: Aphelinidae). In a first bioassay, parasitism rates and parasitoid development were investigated in different host species. The wasp A. ervi was tested on Macrosiphum euphorbiae, Rhopalosiphum padi, and Myzus persicae (Hemiptera: Aphididae) and A. abdominalis was tested on M. persicae, R. padi, and Rhopalosiphum maidis (Hemiptera: Aphididae). The results indicated that A. ervi had a greater percentage of emergence, higher percentage of parasitized aphids, longer developmental time, and higher proportion of females in M. persicae than in the other hosts. A. abdominalis had a greater percentage of emergence, larger progeny, and shorter developmental time in R. padi than in the other hosts. A second bioassay evaluated the preference of the parasitoids for different instars of their respective optimum host aphids in terms of parasitism and development, as determined in the first bioassay. The results showed that A. ervi produced a greater number of mummies in the fourth instar and in adults of M. persicae. In contrast, A. abdominalis preferred the first instar of R. padi. In conclusion, our results indicate that both parasitoid species exhibit different parasitism parameters depending upon the host species and the host stage. This suggests that these parasitoid species could be potentially complementary on multiple or combined releases of biological control programs.