ABSTRACT Mango (Mangifera indica L.) is a tropical fruit of great importance in the world. However, fruit postharvest losses are caused by anthracnose, a disease caused mainly by phytopathogenic fungi from the Colletotrichum genus. Thus, this work aimed to study morphology, genetic similarity, and pathogenicity of Colletotrichum spp. isolates from mango in Rio Grande do Norte state, Brazil. Morphological evaluation of 28 isolates, based on colony color, size of conidia and appressoria, and growth rate, showed that the isolates belong to the C. gloeosporioides species. It was later confirmed with species-specific oligonucleotides. Also, combined evaluation with RAPD (Random Amplified Polymorphic DNA) and ISSR (Inter Simple Sequence Repeats) showed a genetic similarity of 0.23 between Isolates 12 and 21, and 0.71 between Isolates 2 and 4, an indication of high variability among isolates, with dissimilarity over 75%. Moreover, the dendrogram generated by the UPGMA method indicated that the isolates were arranged in eight groups, which did not correlate with the collection site. Based on pathogenicity, although most isolates showed low virulence for Tommy Atkins cultivar, some of them proved to be highly aggressive (Isolates 9, 15, 20, 21, 24, 26, and 27). Also, pathogenicity did not correlate with clusters. In conclusion, the results revealed high genetic and pathogenic variability in C. gloeosporioides isolated from mango cultivars in one of the main exporting regions in Brazil.