Digestive proteolytic and amylolytic activities and feeding responses of fifth instar larvae of Helicoverpa armigera (Hübner) on different host plants including chickpea (cultivars Arman, Hashem, Azad, and Binivich), common bean (cultivar Khomein), white kidney bean (cultivar Dehghan), red kidney bean (cultivar Goli), cowpea (cultivar Mashhad), tomato (cultivar Meshkin), and potato (cultivars Agria and Satina) were studied under laboratory conditions (25 ± 1°C, 65 ± 5% RH and a photoperiod of 16:8 [L:D] h). Our results showed that the highest protease activity in optimal pH was on cultivar Dehghan (8.717U/mg) and lowest one was on Meshkin (3.338 U/mg). In addition, the highest amylase activity in optimal pH was on cultivar Dehghan (0.340 mU/mg) and lowest was on Meshkin (0.088 mU/ mg). The larval weight of fifth instar H. armigera showed significant difference, being heaviest on Binivich (125.290 ± 5.050 mg) and lightest on Meshkin (22.773 ± 0.575 mg). Furthermore, the highest and lowest values of food consumed were on Goli (362.800 ± 27.500 mg) and Satina (51.280 ± 4.500 mg), respectively. In addition, the lowest values of prepupal and pupal weight were on Meshkin (32.413 ± 0.980 and 41.820 ± 1.270 mg, respectively). The results indicated that tomato (Meshkin) was unsuitable host for feeding fifth instar larvae of H. armigera.