The Tomo River runs west to east through the high savannah, known as the 'Altillanura' in eastern Colombia, to flow directly into the Orinoco River. This updated ichthyological checklist was developed by revising and deleting five bibliographic references in combination with the results of an expedition carried out in April 2017 in the lower part of the sub–basin. Here we report 305 species of fish belonging to 183 genera, 45 families and 14 orders. The consolidated checklist includes 69 additional species for Tomo River, of which three species are new records for the Orinoco River basin and eight are new species for Colombia. In addition, we add 578 catalog numbers (10,423 specimens) to the fish collection of the Humboldt Institute (IAvH–P)