Little is known about phenotypic plasticity in guppies and whether it can take on functional roles as it appears to in other fishes. We tested for morphological plasticity in Poecilia reticulata reared under different feeding orientations. Newborn guppies from a stock population originating from Trinidad were assigned to one of five food treatments: (1) surface-floating food, or food adhered to plates; (2) at the surface facing down; (3) midwater facing vertically; (4) on the bottom facing up; or (5) all four orientations on alternate days. Male guppies reared under the floating food regime had shallower and longer bodies, longer skulls, and median paired fins that were longer and thinner than those reared under any other treatment. Females displayed no such diversification. Morphological differences in males between the floating and bottom feeders correspond, respectively, to open water (fusiform) and benthic (deeper-bodied) forms described both among and within many fish species. Guppies reared under the variable regime displayed intermediate characteristics. Morphologies were correlated with foraging efficiencies, although we cannot rule out an effect of learning. Morphological diversity is relatively easy to induce in guppies without resorting to differences in food type as in other studies of phenotypic plasticity.