Introduction: Most of the bioactive substances isolated from marine seagrass are chemically classified as brominated, aromatics, nitrogen-heterocyclic, nitro sulphuric-heterocyclic, sterols, dibutanoids, proteins, peptides, and sulfated polysaccharides. Seagrass can be used as a foodstuff, animal fodder, fertilizer, and industrial material. Antibacterial agents are the most effective ones in the war against infectious diseases but, with both extensive use and misuse, the emergence of bacterial resistance. The aim of the study was to find the antibacterial activity of the seaweed (Ulva sps) against clinically selected isolates (Klebsiella pneumonia, Salmonella typhi and Streptococcus sp) Materials and Methods: The fresh seaweed Ulva sp. was collected and shade dried then the crude extract was prepared. The pathogenic Klebsiella pneumonia, Salmonella typhi, and Streptococcus sp., was collected. The disc diffusion test and Minimum inhibitory concentration test was done. Results and Discussion: The data was collected and tabulated and the bioactivity of the seaweed extracts was expressed as minimum inhibitory concentration (MIC) The antibacterial activity against the selected isolated Klebsiella pneumonia, Salmonella typhi, and Streptococcus sp. Salmonella typhi was more susceptible for the crude extract of the seaweed (Ulva sps) as the MIC = 30 µg/mL. The extract shows potential bactericidal activities against the different pathogens. Conclusion: The study concluded that the seaweed (Ulva sp) has very good antibacterial activity against the selected isolates (Klebsiella, Streptococcus, Salmonella) and Streptococcus sp had more MIC when compared to other isolate