Tricholoma matsutake, one of the most favorable ectomycorrhizal mushrooms, forms a symbiotic relationship with its host, Pinus densiflora. In this study, co-cultivation of T. matsutake mycelium with bacteria from fairy rings was conducted to explore artificial cultivation. Among the isolates tested, strain B22_9_B28 promoted mycelial growth across five T. matsutake isolates: KMCC05631 from Yangyang-gun (124.23%), KMCC05632 and KMCC05633 from Yeongdeok-gun (127.68% and 156.61%, respectively), and KMCC05634 from Yeongdong-gun (153.31%), and KMCC05644 from Bonghwa-gun (171.59%). 16S rRNA sequence analysis suggested that B22_9_B28 may represent a novel species of Paenibacillus. These results highlight the potential of a new Paenibacillus species with pan-regional growth-promoting effects on T. matsutake mycelium, offering a promising avenue for the artificial cultivation of this valuable mushroom.