Predator-prey interactions are often studied by examining either predator or prey behavior. This focal species approach ignores complexity that may determine the outcome of encounters. We used a dual species analysis to characterize how crayfish size (prey) influenced behavioral interactions between fish (predators) and crayfish. This interaction is particularly important in structuring energy flow patterns in aquatic communities. Fish and crayfish behavior were quantified after small (<30 mm carapace length) or large (>30 mm carapace length) crayfish (Orconectes virilis) were placed in wading pools with shelters and with 1 rock bass (Ambloplites rupestris), 2 yellow perch (Perca flavescens), 2 darters (Etheostoma exile, E. nigrum), or no fish (control).Small crayfish spent less time moving, decreased the number of pincer displays, reduced movement (particularly with rock bass), and increased tailflip frequency compared to large crayfish (with fish present). Neither crayfish size nor fish species present affected time crayfish stayed in shelters. Yellow perch approached crayfish more frequently than other fish. Darters interacted with small crayfish more frequently than larger crayfish, whereas the opposite was true for rock bass and perch. That both predator and prey behavior were influenced by prey size suggests the intensity and frequency of predator-prey interactions are affected by prey size.