The oyster mushroom (Pleurotus ostreatus) is one of the most widely cultivated mushrooms in the world. Nutrients provided in the media is one of the most important factors affecting the growth of mushroom. The present study mainly focuses on the isolation of Mushroom Growth Promoting (MGP) bacteria and studies its effect on the mycelial growth. Nineteen bacteria were isolated from the media of Pleurotus ostreatus and their effect on mycelial growth of the Pleurotus ostreatus was investigated. Based on mycelial growth on solid medium shows difference among treatments in the day taken for the mycelium to cover the petri dish (three days earlier than control). Three bacteria isolate with the best result were identified based on 16S rDNA sequencing and phylogenetic tree construction by the neighbor-joining method using MEGA version 6.06 based on 1 000 × bootstraps and identified as Bacillus cereus strain ATCC 14579, Bacillus aryabhattai strain B8W22 and Acinetobacter pittii strain ATCC 19004. The results of this research strongly suggest that inoculation of the mycelium with specific bacteria supernatant may have beneficial applications for mushroom production.