Based on a rigorous analysis of fish collections of the Instituto Amazónico de Investigaciones Científicas (Sinchi) and new collections by us, we report new Colombian records and geographical range extensions for freshwater fish species. The new occurrences include representatives of four taxonomic orders, eight families, and 13 genera. Our findings expand the geographic ranges of fish species within the Amazon and Orinoco basins and include species reported from Colombia for the first time. This information is fundamental for completion of species inventories, as well as analyses of freshwater fish diversity patterns at macroecological scales. In addition, our data provide useful information for the formulation of strategies for the conservation, management, and sustainable use of biodiversity.