The cotton bollworm, Helicoverpa armigera (Hübner), is one of the most important pests of many host crops in Iran and worldwide. The effect of different cultivars of bean (Phaseolus vulgaris L.) including white kidney bean (cultivars Pak, Daneshkadeh and Shokufa), common bean (cultivar Talash) and red kidney bean (cultivars Akhtar, Sayyad and Naz) was studied on the reproductive parameters of H. armigera under laboratory conditions (25±1 °C, 65 ± 5% RH, and photoperiod of 16: 8 (L: D) h) and on the activity of some digestive enzymes of the larvae under field conditions. The highest rates of gross fecundity and gross fertility were on red kidney bean Naz, and the lowest values of these parameters were on white kidney bean Pak and red kidney bean Akhtar, respectively. The highest rates of net fecundity and net fertility were observed on common bean Talash, whereas the lowest values of these parameters were seen on red kidney bean Akhtar. The lowest proteolytic activity of fourth and fifth instar larvae of H. armigera was respectively on the leaf of red kidney bean Akhtar and red kidney bean Naz. Among the pods of different bean cultivars, proteolytic activity of fourth and fifth instar larvae was the lowest when they were fed on the green pod of red kidney bean Akhtar. The lowest amylolytic activity of fourth and fifth instar larvae of H. armigera was on the leaf of red kidney bean Naz. The fourth and fifth instar larvae reared on the green pod of common bean Talash showed the lowest amylolytic activity. The results indicated that red kidney bean Akhtar was an unsuitable host for H. armigera feeding. The findings of this study could be used in designing new strategies to control H. armigera.