Diaporthe species have often been reported as important plant pathogens, saprobes and endophytes on a wide range of plant hosts. Although several Diaporthe species have been recorded in China, little is known about species able to infect forest trees. Therefore, extensive surveys were recently conducted in Beijing, Heilongjiang, Jiangsu, Jiangxi, Shaanxi and Zhejiang Provinces. The current results emphasised on 15 species from 42 representative isolates involving 16 host genera using comparisons of DNA sequence data for the nuclear ribosomal internal transcribed spacer (ITS), calmodulin (cal), histone H3 (his3), partial translation elongation factor-1α (tef1) and β-tubulin (tub2) gene regions, as well as their morphological features. Three known species, D. biguttulata, D. eres and D. unshiuensis, were identified. In addition, twelve novel taxa were collected and are described as D. acerigena, D. alangii, D. betulina, D. caryae, D. cercidis, D. chensiensis, D. cinnamomi, D. conica, D. fraxinicola, D. kadsurae, D. padina and D. ukurunduensis. The current study improves the understanding of species causing diebacks on ecological and economic forest trees and provides useful information for the effective disease management of these hosts in China.