The tomato leaf miner, Tuta absoluta, is one of the most destructive pests on tomato croup that could be imposed up to 100% of yield loss. The predatory bug, Nabis pseudoferus and the parasitoid Trichogramma brassicae are the natural enemies of this pest. Since the interaction between predators and parasitoids in different trophic levels such as intraguild predation can decrease or increase the efficiency of natural enemies, the effects of age dependent parasitism of host eggs on IGP between these two species were investigated under the laboratory condition (25±1°C, 70±10% RH, 16L: 8D). In no-choice and choice preference tests, the predatory bug was exposed to 40 parasitized and non-parasitized eggs with different ages (24, 48 and 72 h-old). Switching test with different combinations of tomato leaf miner eggs (30:90, 45:75, 60:60, 75:45, and 90:30 non-parasitized eggs: parasitized eggs) was also estimated at the mentioned times. In no choice test, the highest feeding rate of predatory bug was 39.21±0.36 eggs on 24 h-old non-parasitized eggs and the lowest feeding rate was 1.4±0.80 eggs on 72 h-old parasitized eggs. In choice test, comparison of the Manly’s β index indicated that predator bug preferred non-parasitized eggs than parasitized eggs in 48 and 72 h-old eggs (respectively, (non-parasitized 0.59 ± 0.01, parasitized 0.40 ± 0.01) and (non-parasitized 0.90 ± 0.009, parasitized 0.09 ± 0.009)), but there was no significant difference between Manly’s β index for 24 h-old eggs (non-parasitized 0.48 ± 0.01, parasitized 0.51 ± 0.01). Results of switching test showed that the linear regression between Manly’s β index and different ratios of non-parasitized eggs to parasitized and non-parasitized eggs was not significant in 72 h-old eggs. However, this regression was significant in 24 and 48 h-old eggs and the predator's preference was depended to the relative frequency of tomato moth eggs. Results of this study showed that the increasing age of parasitized egg decreased intensity of IGP between Nabis pseudoferus and Trichogramma brassicae.