Abstract: The experiment was conducted to determine the effect of host age and photoperiod on the parasitism of Trichogrammatoidea bactrae (Hymenoptera: Trichogrammatidae). Pink Bollworm (PBW, Pectinophora gossypiella (Lepidoptera: Gelechiidae) eggs were used as host. The host eggs of different ages (1, 2, 3, 4 and 5 days old) were exposed to two pairs of the parasitoid (T. bactrae) at two light/dark regimes (complete light & complete darkness) with constant 75% relative humidity and 28 °C temperature. It was observed that under the conditions of this test, maximum parasitization, > 90% by T. bactrae, was obtained when 1 or 2 days old host (PBW) eggs were held in complete light.