Öz Eretmocerus warrae Naumann and Schmidt is a thelytokous parasitoid that attacks the greenhouse whitefly, Trialeurodes vaporariorum. Its host discrimination and superparasitism behavior was investigated at different host densities and time intervals between the first and second ovipositions under laboratory conditions (22 ± 1 °C, 60 ± 5% RH, a 16:8 light:dark photoperiod). At a density of between 10 and 15 hosts, significantly fewer ovipositions in parasitized nymphs were performed by the same experienced parasitoids (SEPs) or by different experienced parasitoids (DEPs) than by naïve parasitoids (NPs) 1 and 24 h after parasitization by the first female. However, at a host density of 15 nymphs, SEPs, NPs, and DEPs allocated significantly fewer eggs in the parasitized hosts than at that a density of 10 nymphs. Our results also showed that with the increase of host density from 20 to 140, the superparasitism rate of E. Warrae significantly decreased. The findings from this study in relation to the mass rearing of E. Warrae or field release are discussed.