“Endosymbiosis” is a cohesive form of a symbiotic association. Endobacteria exist in many fungiplay important roles in fungal host biology. Metarhizium spp. are important entomopathogenic fungi for insect pest control. In the present study, we performed comprehensive ana­lyses of strains of Metarhizium bibionidarumM. anisopliae using PCR, phylogenetics,fluorescent electron microscopy to identify endobacteria within hyphaeconidia. The results of the phylogenetic ana­lysis based on 16S rRNA gene sequences indicated that these endobacteria were the most closely related to Pelomonas puraquaeaffiliated with Betaproteobacteria. Ultrastructural observations indicated that endobacteria were coccoidless than 500‍ ‍nm in diameter. The basic characteristics of endobacteria in M. bibionidarumM. anisopliae were elucidated,biological questions were raised regarding their biological functions in the Metarhizium hosts.