A taxonomic review of the hornwort genera "Dendroceros" Nees and "Megaceros" Campb. in Thailand is presented, based on herbarium specimens and field surveys. Three species are recognized, namely "D. cucullatus" Steph., "D. suplanus" Steph. and "M. flagellaris" (Mitt.) Steph. A key, descriptions and line drawings and notes on the ecology and geographical distribution of the species are provided.