In April 2019, Samanea tubulosa seedlings were observed with typical anthracnose symptoms in a forest nursery in São João Evangelista, Minas Gerais, Brazil. Based on morphological characteristics and phylogenetic analyses of ITS (5.8 S ribosomal RNA and the flanking internal transcribed spacer regions), act (actin), cal (calmodulin) and gapdh (glyceraldehyde-3-phosphate dehydrogenase) sequences, the fungus was identified as Colletotrichum karstii. Inoculation of the fungus in healthy S. tubulosa seedlings showed symptoms similar to those observed under natural conditions. To our knowledge, this is the first report of C. karstii causing anthracnose in S. tubulosa worldwide.