Endophytic fungi are an intriguing group of host-associated microorganisms that enhance plant growth and fitness by producing bioactive secondary metabolites. These fungi serve as valuable sources of industrial enzymes for secondary metabolite synthesis, benefiting green agriculture, biotechnology, and pharmaceuticals. Despite the economic and ecological significance of the Itea genus—known for its rare sugar content—its associated endophytic fungi remain undocumented. This study isolated and characterized 11 strains of endophytic fungi, primarily identified as pestalotioid taxa, from the leaves, stems, and roots of Itea japonica and I. riparia in Chiang Mai Province, Thailand. Using morphological analysis, multiloci phylogeny (ITS, tub2, tef1-α), and nucleotide polymorphism studies, researchers proposed Neopestalotiopsis iteae and Pseudopestalotiopsis iteae as new species inhabiting I. japonica and I. riparia, respectively. Additionally, Neopestalotiopsis chrysea, N. haikouensis, and Pestalotiopsis jinchanghensis were identified as new records on I. riparia.