Fungal members of Colletotrichum (Ascomycota) were found to be associated with Chordodes formosanus, one of the three currently known horsehair worm (Nematomorpha) species in Taiwan. The fungi were identified as Colletotrichum fructicola, which is mostly known as a plant pathogen, through the use of the nuclear ribosomal internal transcribed spacer and partial large subunit (nrITS + nrLSU) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) DNA sequences. To our knowledge, this report represents both the first records for Colletotrichum associated with hairworms and for fungi on Nematomorpha. These findings expand the knowledge on the ecological relationships of both clades.