Vialaea comprises endophytic as well as phytopathogenic species, the later forming cankers on two economically important and ornamental host plant species. A strain of Vialaea was isolated from dead Mangifera indica twigs in Chiang Rai Province, in northern Thailand. Phylogenetic analysis of ITS and LSU sequence data shows that this is a hovel species, which groups with Vialaea species forming a distinct clade, and supports Vialaeaceae as a distinct family in Xylariales. The new species, introduced as Vialaea mangiferae is described, illustrated and compared with other species in the genus. Vialaea mangiferae differs from other Vialaea species in having 3-5 clustered perithecia in pseudo-stromatic tissues and a peridium with globose cells. The asexual state of Vialaea, which formed in culture, is reported for the first time.