The efficiency of natural enemies as the key factor in success of any biological control programs, depends on different elements including the quality of their herbivore hosts. Similarly, it may be influenced by nutritional status of host plants in turn. This study was undertaken to determine the parasitism capacity of Trichogramma principium (Sugonjaev&Sorokina) on Helicoverpa armigera (Hüb.) reared on different nitrogen fertilized tomato plant cultivars. All experiments were established in a growth chamber at laboratory conditions (25 ± 1 °C, 60 ± 5% RH 16:8 (L:D) h). Six cultivars including Kingston (K), Riogrand (RG), Earlyurbana (E), Redston (R), Superstrain-B (SB) and Primoearly (P), with four N levels, were evaluated in 5 replications. The nitrogen fertilization regime consisted of (n0=0 Kg / h-1, n- = 210 Kg / h-1, ns = 300 Kg / h-1, n+ = 390 kg Ha-1N as Urea 46%). Parasitism data were analyzed using the CONSUME-MSChart as designed by Chi (2017). The means, variances, and standard errors of parasitism parameters were estimated with the bootstrap method. The value of the net parasitism rate (C0) of T. principium varied from 3.42±1.04 to 15.39±2.59 on H. armigera reared on En0, and SBn+, respectively. The transformation rate from host population to parasitoid offspring (Qp) on all treatments was close to 1 (C0≅R0). The total parasitism capacity of a stable population (ѱ) ranged from 0.1392±0.023 to 0.2551±0.031 host/parasitoid on H. armigera reared on En0 and SBn+, respectively. The finite parasitism rate (ω) considers the finite rate of increase ( ), the stable age-stage distribution( ) , and the age-stage specific parasitism rate( ) thus, this parameter could be used to determine the efficiency of a parasitoid. The lowest observed values of (ω) included 0.1748, 0.1660, 0.1653, 0.1649, 0.1540 & 0.1525 hosts parasitoid-1 day-1 on hosts reared on K, P, RG, SB, R & E in their lowest N treatments, respectively; however, the highest (ω) was 0.2948, 0.2624, 0.2421, 0. 3164, 0.2622 & 0.2423 hosts parasitoid-1 day-1 which were observed on the same treatments with their highest N level, respectively. In general, T. principium had higher parasitism capacity on hosts reared on SB, K and RG + highest N levels, which were more suitable for parasitoid. This study showed that parasitism capacity of parasitoid was positively correlated with nitrogen fertilizer treatments.