The cotton bollworm, Helicoverpa armigera (Hübner), which is known as one of the most important economic pests, can cause severe damage to different crops in Iran and many countries of the world. The effect of five maize hybrids: SC260, SC500, SC700, SC704 and DC370 on lysozyme activity in the hemolymph of sixth instar of H. armigera using lytic zone assay and its association with some fitness parameters of this pest was studied in growth chamber (25 ± 1˚C, 65 ± 5% RH and a photoperiod of 16:8 (L : D) h). Our results indicated that except on SC260, the frequency of high immune-activated larvae on the other maize hybrids was lower than that of low immune-activated larvae. The mean lysozyme concentration in H. armigera larval hemolymph was the highest on SC260 (0.096 ± 0.01 mg/ml) and lowest on DC370 (0.060 ± 0.007 mg/ml). The longest pupal period was on SC500 (12.00 ± 0.49 days) and the shortest was on SC700 (10.37 ± 0.19 days). Daily and total fecundities of H. armigera were the highest on DC370 (61.68 ± 9.85 and 196.89 ± 49.30 eggs, respectively) and lowest on SC260 (20.60 ± 5.88 and 52.71 ± 18.80, respectively). The results of this study can provide fundamental information for management of H. armigera on maize hybrids.