Pectinatella magnifica is a freshwater bryozoan, which has become a subject of scientific interest because of its invasive expansion worldwide. To obtain a comprehensive overview of its influence on environments, information on associated bacteria is needed. In this study, cultivable bacteria associated with P. magnifica were investigated. In total, 253 isolates were selected for preliminary identification by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry and clustered based on repetitive extragenic palindromic-PCR profiles. Among these, 169 strains were selected and identified using 16S rRNA gene comparative analyses. The sequences were grouped into 76 phylotypes and affiliated with 67 species. The majority of isolated bacteria belonged to Gammaproteobacteria, followed by Betaproteobacteria, Firmicutes, Bacteroidetes and Actinobacteria. Most strains within the Betaproteobacteria were isolated exclusively from bryozoan colonies. Aeromonas was the genus predominantly isolated from both P. magnifica and the water samples. Based on 16S rDNA similarity values, 15 putative new species belonging to the genera Aeromonas, Aquitalea, Clostridium, Herbaspirillum, Chromobacterium, Chryseobacterium, Morganella, Paludibacterium, Pectobacterium, Rahnella, Rhodoferax and Serratia, and putative new genera belonging to families Clostridiaceae and Sporomusaceae were revealed. The majority of the detected bacteria were species widely distributed in the environments; nevertheless, a possible symbiotic association of two new putative species with P. magnifica cannot be excluded.