Phylogenetic relationships among isolates of Cercospora species pathogenic to water hyacinth, collected from several geographic regions of the world, were examined by using partial DNA sequences from three protein-coding genes: elongation factor-lα, β-tubulin, and histone H3. In cladograms from individual, as well as from combined datasets for 14 isolates, two statistically well supported clades were found: a mijor clade that included isolates from Brazil, Venezuela, Mexico, Florida (USA), South Africa, and Zambia; and a minor clade restricted to isolates from Texas (USA). Shape and dimensions of conidia were unreliable criteria for taxonomic differentiation of most isolates that composed the two clades. In addition, the ex-type culture of C. rodmanii did not show differences in DNA sequence in relation to the other isolates grouped in the major clade, including some that had conidial size and morphology fitting the description of C. piaropi. Therefore, the separation of these species not only did not have strong phenotypic support, but also did not have support from the phylogenetic analysis. Consequently, the description of C. piaropi is emended herein to include C. rodmanii as a synonym.