Abstract: In this study midstream urine samples were collected from urinary tract infected patients to isolate and identify UTI causing bacterial pathogens by biochemical methods. The identified strains were two gram-positive and five gram-negative bacterium. Out of these we have selected one gram-negative (Staphylococcus aureus) and three gram-positive (Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumoniae) bacteria for current study. The antibacterial effect of aqueous, hexane, chloroform, ethyl acetate and methanol extracts of Avicennia marina against UTI pathogens were studied. Most effective three extracts of A. marina were treated with charcoal. Out of three extracts methanol was confirmed as tremendous to act against bacterial isolates and it was characterized at two different concentrations and compared with chemical based antibiotics. The stability and antimicrobial efficacy of the extract of A. marina in different parameters such as temperature, pH, enzyme, surfactant, organic solvent was determined. In summary, the extract showed an excellent stability and effectiveness to temperature 50°C, pH 4, enzyme treatment using protease, surfactant (EDTA) and organic solvent (formaldehyde).