The IUCN Red List of Threatened Species uses geographical distribution as a key criterion in assessing the conservation status of species. Accurate knowledge of a species’ distribution is therefore essential to ensure the correct categorization is applied. Here we compare the geographical distribution of 35 species of chameleons endemic to East Africa, using data from the Global Biodiversity Information Facility (GBIF) and data compiled by a taxonomic expert. Data screening showed 99.9% of GBIF records used outdated taxonomy and 20% had no locality coordinates. Conversely the expert dataset used 100% up-to-date taxonomy and only seven records (3%) had no coordinates. Both datasets were used to generate range maps for each species, which were then used in preliminary Red List categorization. There was disparity in the categories of 10 species, with eight being assigned a lower threat category based on GBIF data compared with expert data, and the other two assigned a higher category. Our results suggest that before conducting desktop assessments of the threatened status of species, aggregated museum locality data should be vetted against current taxonomy and localities should be verified. We conclude that available online databases are not an adequate substitute for taxonomic experts in assessing the threatened status of species and that Red List assessments may be compromised unless this extra step of verification is carried out.