In tropical floodplains, rivers have a high dynamic in space and time, which are determinants in the organization and trophic structure of fish assemblages. We evaluated the influence spatial and temporal on the trophic structure of fish assemblages in the sediment banks of the Bananal floodplain, in the Middle Araguaia river region. We identified the food preferences of the species by the analysis of the stomach content of 564 individuals distributed in 48 species of 22 families and six orders. We classified fish assemblages into eight trophic groups according to the Alimentary Index (IAi). Analysis of the abundance and richness of the trophic groups indicated that fish assemblage trophic structure varied between environments the seasonal periods. Our results suggest that the composition and distribution of the fish trophic groups in the sediment banks of the Bananal floodplain are structured by spatial gradient and temporal. Together, the space and time determine high variability in the trophic organization of the fish fauna in these environments.