Camellia sinensis (L.) O. Kuntze, commonly known as tea, is widely cultivated around the world in tropical and subtropical areas. Tea is mainly manufactured using young shoots of tea plants. Therefore, it is essential to control foliar diseases. Gray blight disease is caused by pestalotiopsis-like taxa and is known as one of the most destructive tea diseases. Although several studies have provided the groundwork for the fungal diseases associated with C. sinensis in Taiwan, gray blight disease has not been characterized based on diversity, molecular systematics, or pathogenicity. The goal of this study was to identify and characterize the causative agents of tea gray blight disease. A total of 98 pestalotiopsis-like isolates associated with symptomatic leaves of C. sinensis from major tea fields in Taiwan were investigated. Based on phylogenies of single and concatenated DNA sequences (internal transcribed spacer, β-tubulin, translation elongation factor 1-α) together with morphology, we resolved most of the pestalotiopsis-like species in this study. The study revealed seven well-classified taxa and seven tentative clades in three genera: Pestalotiopsis, Pseudopestalotiopsis, and Neopestalotiopsis. One novel species, Pseudopestalotiopsis annellata, was introduced. Five new records, Pseudopestalotiopsis chinensis, Pseudopestalotiopsis camelliae-sinensis, Pestalotiopsis camelliae, Pestalotiopsis yanglingensis, and Pestalotiopsis trachicarpicola, were introduced for the first time in Taiwan. Pseudopestalotiopsis chinensis was the taxon most frequently isolated from C. sinensis in this study. Furthermore, results of pathogenicity assessments exhibited that, with wound inoculation, all assayed isolates in this study were pathogenic on tea leaves. Pseudopestalotiopsis chinensis and Pseudopestalotiopsis camelliae-sinensis were identified as the major pathogens associated with gray blight disease of tea in Taiwan. To our knowledge, this is the first study of the diversity, pathogenicity, and characterization of pestalotiopsis-like fungi causing tea gray blight disease in Taiwan.