Resource assessments of small-scale fisheries in the Amazon are rare, making it difficult to improve fisheries management. This study assessed the sustainability of small-scale fishery resources in the Lower Amazon region using data from over 20,000 interviews collected in three floodplain fishing communities between 1992 and 2007. The data were analyzed with respect to theoretical maxima of catches and historical trends of (i) catch per unit effort (CPUE), (ii) species composition of the catch, and (iii) mean body length of the most-caught species. The most important results were: First, observed catches have been about 54–58% of theoretical maxima in all communities. Second, CPUE has remained stable over time in all communities. Third, there has been no substitution of fish species in the catch. Fourth, mean body lengths of five of the nine most-caught species were below length-at-first-reproduction, and the body lengths of some have increased overtime while that of others have remained stable or decreased. Overall, fishery resources in the region appear to be moderately exploited, with some key species showing typical signs of overexploitation. This would indicate that the principal threat to the sustainability of fishery resources is excessive concentration of fishing effort on a few target species combined with unsustainable fishing practices. Management and research recommendations are proposed.