The study was conducted on the biological parameters of Trichogramma chilonis Ishii (Trichogrammatidae: Hymenoptera) feeding on grain moth, Sitotroga cereallela eggs at three constant temperatures and five different ages of host eggs at Insect Pest Management Programme, National Agricultural Research Centre, (NARC) Islamabad. The results revealed that maximum rate of parasitism was 95.70 ± 1.94 at 28 ± 1 °C while minimum was 61.30 ± 1.70 at 32 ± 1 °C. Maximum adult emergence and female ratio from parasitized eggs were 96.30% with 59.2± 5.83 female ratio at 28 ±1 °C while minimum was 51.10% with female ratio of 58.1 at 32±1 °C. The maximum developmental duration (9.6 ± 0.32 days) and adult longevity (4.3 ± 0.38 days) was at 24 ±1 °C while minimum was 7.4 ±0.36 and 2.0 ±0.56 days at 32 ± 1 °C. The results indicate that temperature has a significant effect on the biological parameters of Trichogramma and with increasing temperature developmental duration decreased. Similarly effect of host eggs age indicates that maximum parasitism and adult emergence were 97.40 ± 0.84% and 98.20 ± 0.94% on 2h old eggs while minimum parasitism was 24.6 ± 4.92% and adult emergence was 21.5 ± 1.33% from 72h old eggs. Adult longevity and female ratio was not significantly different at different ages of host eggs. Thus out of three tested temperatures, 28 ±1 °C was more suitable for mass rearing of Trichogramma and feeding 2-12h old eggs for maximum parasitism and adult emergence from parasitized eggs under laboratory condition of 28 ±1 °C.