We studied the great evening bat (Ia io) in India (Meghalaya) and China (Guizhou), and present the 1st account of its feeding behavior. We analyzed droppings collected from 119 bats between November and May 2001–2002 and 2002–2003 from India; 28 included bird feathers, with most of these containing 90–100% feathers by volume. The main constituent of the diet overall was Coleoptera, although Lepidoptera and traces of Diptera, Orthoptera, and Hemiptera also were found. In China, bats were captured in early November, and fresh droppings also were collected from underneath the roost. Bird feathers comprised 82% of the droppings of bats by volume. I. io emits relatively low-frequency echolocation calls and sometimes produces 2-toned calls, a characteristic of species that echolocate distant targets. I. io has a high wing loading (15.4 Nm⁻²), average aspect ratio (6.9), and a high tip shape index (1.1), features associated with fast efficient flight. Phylogenetic analysis of a concatenation of mitochondrial ND1 and cytochrome-b genes indicated that I. io is phylogenetically close to Scotomanes ornatus, in a clade (Nycticeiini) distinct from bats in the genus Pipistrellus with which it has been previously allied. Although I. io converges in wing shape and echolocation call design with the carnivorous, fast-flying Nyctalus lasiopterus, its carnivorous behavior likely evolved independently because the 2 species are not close relatives. It is unlikely that I. io captured birds nesting or roosting at the study caves, and its morphology and echolocation behavior seem well adapted for the capture of large aerial insects and flying birds.