Abstract We tested the hypothesis that the highly flexible feeding repertoire of juvenile Chaetodipterus faber reflects their trophic adaptability by quantifying the feeding behaviour of juveniles in situ, for the first time, in a northeastern Brazilian estuary. The fishes presented a preference for alga-rich habitats, irrespective of the substrate type chosen during feeding bouts. The analysis of stomach contents revealed omnivorous feeding habits, indicating that the ingestion of plant material occurs incidentally during foraging for benthic prey hidden under the alga. Particulate feeding in the water column was often as important as bottom feeding on alga-rich substrates. The results of this study are consistent with those of other ephippid species in different coastal environments, which typically exploit an ample diversity of food items from different substrates. Therefore, the flexibility observed in the feeding behavior of the most ephippid species may be a fundamental determinant of the ecological success of this group.