In this study raw and branded milk samples were collected and were processed for the isolation and identification of Listeria monocytogenes. The experimental results shows that the presence of Listeria monocytogenes in raw as well as branded milk samples. This research indicated that the milk samples had significant effects on the bactericidal power of ozone against non-spore former, Gram positive bacilli Listeria monocytogenes. The ozonation treatment was to eliminate only the L. monocytogenes and there was no change in nature of milk that is color, temperature, pH and the nutritional values such as protein, carbohydrate, and calcium. So the ozonation treatment in milk is highly recommended in dairy industries. Further research is required to ascertain the precise mechanism of the application of ozonation for the milk samples.