Water hyacinth (Eichhornia crassipes) is a free floating invasive/aggressive aquatic macrophyte that is known to pose a grave threat to aquatic environment. Because of its rapid growth, it can obstruct access to the pumps used for irrigation, causing water resources depletion, and the spreading of mosquitoes and flies which are vectors of several diseases, therefore, it tends to eliminate all other organisms in surrounding. Various utilization methods have been employed among which using the biomass for different purposes via vermicomposting process is recommended. The aim of this study was to investigate bacterial dynamics in the vermicomposting process using water hyacinth biomass collected from Lake Tana. Vermicompost was prepared using water hyacinth, cow manure, sawdust, biochar and earthworm at different proportion (treatments) and bacteria isolated from different treatments. The isolates were then characterized using the traditional cultural methods (morphological and biochemical). Differences were considered significant at p < 0.05. Colony forming unit (CFU/g), Operational Taxonomic Units and the identified genera were used to compare the different microbial populations at the different treatments of the vermicompost process. Based on the result of this study, significant variation of microbial counts among the different treatments of vermicompost (P < 0.05) was observed. The highest (i.e. 2.79 × 108 (CFU/g) viable of bacteria count was found from T3 (which contain basal substrate, earthworm and biochar) and the lowest (i.e. 2.23 × 108 (CFU/g)) viable of bacteria was recorded on T10 (which contain only basal substrate). Presumptive identification of the isolates indicated that they were related to the genus Bacillus (27%), Pseudomonas (23%), Micrococcus (13%), Azotobacter (11%), Neisseria (9%) and Aeromonas (10%), Escherichia (5%), Enterobacter (2%). Genera of Bacillus and Pseudomonas constitute half of total isolates and the result of this study suggesting that vermicomposting may enhance the population of beneficial microbes which could be helped in degradation processes via the production of excellent biofertilizer. Key words Bacteria, biochar, cow manure, sawdust, vermicompost, and water hyacinth