We compared rates of leaf-litter breakdown between aquatic and terrestrial habitats in an Amazonian watershed characterized by seasonal backwater flooding. Leaves of two tree types, Inga sp. (Fabaceae) and Triplaris sp. (Polygonaceae) were incubated for 101 days in three sites with different flooding regimes:  permanently submerged, intermittently flooded, and unflooded terra firme.  Litterbags of two mesh sizes were used to compare the presence versus absence of macroinvertebrates on leaf breakdown.  Triplaris leaves generally decomposed at a faster rate and displayed greater disparities between coarse and mesh leafpacks than Inga.  Triplaris breakdown was considerably higher in unflooded habitats with macroinvertebrates. Inga breakdown was slowest in permanently submerged environments.  In terra firme and intermittently flooded environments, both coarse and fine mesh Inga treatments had similar breakdown rates indicating macroinvertebrates may have little effect on turnover of this leaf species. The average leaf-litter breakdown rate for all of the treatments fell within the range of breakdown rates recorded from other terrestrial and aquatic habitats in the tropics. The results of this study suggest that, in tropical systems with seasonal backwater flooding, leaf breakdown rates are influenced by tree species, the suite of decomposing organisms, and the flooding regime.