During our investigations of the microfungi on medicinal plants in Thailand, five isolates ofDiaporthewere obtained. These isolates were identified and described using a multiproxy approach, viz. morphology, cultural characteristics, host association, the multiloci phylogeny of ITS,tef1-α,tub2,cal, andhis3, and DNA comparisons. Five new species,Diaporthe afzeliae,D. bombacis,D. careyae,D. globoostiolata, andD. samaneae, are introduced as saprobes from the plant hosts, viz.Afzelia xylocarpa,Bombax ceiba,Careya sphaerica, a member of Fagaceae, andSamanea saman. Interestingly, this is the first report ofDiaporthespecies on these plants, except on the Fagaceae member. The morphological comparison, updated molecular phylogeny, and pairwise homoplasy index (PHI) analysis strongly support the establishment of novel species. Our phylogeny also revealed the close relationship betweenD. zhaoqingensisandD. chiangmaiensis; however, the evidence from the PHI test and DNA comparison indicated that they are distinct species. These findings improve the existing knowledge of taxonomy and host diversity ofDiaporthespecies as well as highlight the untapped potential of these medicinal plants for searching for new fungi.