We studied insectivory by five carnivores—the Asiatic black bear (Ursus thibetanus), Japanese marten (Martes melampus), Japanese badger (Meles meles), red fox (Vulpes vulpes), and raccoon dog (Nyctereutes procyonoides)—in a cool-temperate deciduous forest in Japan. From May 2003 to April 2005, we assayed 373 fecal samples (91 from bear, 158 from marten, 43 from badger, 36 from fox, and 45 from raccoon dog) for insects. Each carnivore species consumed a variety of insect species, some preferentially. Bears preferred colonial insects like ants and wasps; martens ate a variety of forest insects, such as ground beetles and arboreal insects; badgers preferred forest ground beetles; foxes ate ground beetles and grassland insects; and raccoon dogs ate a variety of species. Dietary preferences may reflect the feeding strategy, behavior, or habitat preference of each carnivore species. Based on the habitat preferences of the insects, we could assign carnivores to particular microhabitats: bears and martens used forest in three dimensions, badgers inhabited forest in two dimensions, foxes used grassland and forest in two dimensions, and raccoon dogs inhabited grassland and forest in three dimensions. Identification of insects in feces may provide information on the dietary and habitat preferences of these carnivores.