Nitrate NO(3)(-) contamination of groundwater resources is a serious problem. Such contamination in drinking water is regulated by environmental agencies around the world since at higher concentrations it can cause several health problems in infants. The aim of the present study was to identify the efficiency of the bacterial species isolated from nitrate-contaminated water and soil samples collected from Erode, Salem, Dharmapuri, and Krishnagiri districts of Tamilnadu, India. There are 74 morphologically different bacterial species were isolated and evaluated by a dissimilatory and assimilatory nitrate reduction test. Among the isolates, DW-27, DS-29, DS-31, DS-45, DS-46, and DS-47 were found to be potential dissimilatory and EW-6, ES-15, DS-39, DS-41, DS-48, DS-55, and SW-59 were potential assimilatory nitrate reducers. The results of bacterial analysis revealed that the isolated nitrate-reducing bacteria belonged to the genera Bacillus (64%) and Corynebacterium (22%), family Enterobacteriaceae (11%), and genus Alcaligenes (3%). This observation has led to the conclusion that these bacterial species showed efficiency of nitrate removal.