We analyzed invertebrate abundance and richness associated with decomposing litter across three riverine wetlands with different inundation regimes located in the alluvial floodplain of the Paraná River. Three replicate bags were incubated for different types of leaf litter that were dominant in each wetland for five sampling dates, yielding a total of 165 litterbags. The number of invertebrates per g of remaining leaf litter differed among wetlands and was affected by leaf litter type and incubation date within each wetland. In contrast to abundance, differences in invertebrate composition were more pronounced across wetlands than across leaf litter types within a wetland. Different species dominated in each of the three wetlands. When we compared the number of invertebrates per g remaining of a single litter type (Eichhornia crassipes) across the three wetlands, variability in density was explained by the NH₄ content of the water and dissolved oxygen concentration. Many invertebrates associated with litter may not be directly involved in shredding the material, and collectors dominated invertebrate assemblages at study sites. Although both litter quality and wetland condition affect the invertebrates colonizing leaf litter, our results suggest that spatial heterogeneity, linked to connectivity, plays an important role in determining invertebrate assemblages.