True bugs (Hemiptera) are an important pest complex not controlled by Bt-transgenic crops. An alternative source of resistance includes inhibitors of digestive enzymes, such as protease or amylase inhibitors. αAI-1, an α-amylase inhibitor from the common bean, inhibits gut-associated α-amylases of bruchid pests of grain legumes. Here we quantify the in vitro activity of α-amylases of 12 hemipteran species from different taxonomic and functional groups and the in vitro inhibition of those α-amylases by αAI-1. α-Amylase activity was detected in all species tested. However, susceptibility to αAI-1 varied among the different groups. α-Amylases of species in the Lygaeidae, Miridae and Nabidae were highly susceptible, whereas those in the Auchenorrhyncha (Cicadellidae, Membracidae) had a moderate susceptibility, and those in the Pentatomidae seemed to be tolerant to αAI-1. The species with αAI-1 susceptible α-amylases represented families which include both important pest species but also predatory species. These findings suggest that αAI-1-expressing crops have potential to control true bugs in vivo.