Evaluations of the functioning of benthic marine food webs could be improved by quantifying organic matter fluxes from the meiofauna to higher trophic levels. In this study, we measured the simultaneous ingestion of meiofauna and macrofauna by common dwellers of a tropical intertidal mudflat on the coast of Amazonia. The meiofauna and macrofauna (tanaid) communities of a tropical intertidal mudflat of French Guiana were separately enriched with 15N and 13C, respectively. The enriched preys were then used as tracers during feeding experiments with common predators of different sizes and feeding mechanisms: a Portunidae crab (Callinectes bocourti), a Penaeidae shrimp (Farfantepenaeus subtilis), and a Gobiidae fish (Gobionellus oceanicus). In feeding experiments with all predators except crabs, feeding rates increased with the availability of meiofauna and macrofauna food sources. The ability of consumers to ingest their food selectively was evaluated by calculating the differences in the ratio of macrofauna to meiofauna between the (1) ingested material and (2) that available in the environment. Larger predators showed a higher degree of preferential macrofauna ingestion than smaller predators, consistent with the optimal foraging theory. For large predators, the meiofauna would be important only during early life or in the absence of large food items.