Excessive growth of cyanobacteria leads to blooms. These blooms severely affect the aquatic ecosystem. This work describes the utilization of these bloom forming Cyanobacteria as potential sources of antibacterial agents. Antibacterial activity is the antagonistic effect exerted by the microbes on other living species. Cyanobacteria have a tendency to produce secondary metabolites which prevent the growth of bacteria.The antibacterial property of these microbes is due to their excellent acumen to produce secondary metabolites which prevent the growth of bacteria. The inhibition of the bacterial growth is by interfering with the protein synthesis, retarding the metabolism and rupturing the cell wall of bacteria. In this study, we have explored the antibacterial potential of two bloom forming cyanobacteria Anabaena variabilis and Synechococcus elongates against clinically isolated human pathogenic gram negative bacteria Escherichia coli, Enterococcus sp., Klebsiella sp. Exploring Cyanobacteria for antibacterial property can help us in their application as antimicrobial drug and thus prevent the various problems related to drug resistance and side effects of present day drugs.