Abstract: In-vitro antibacterial activity of marine ascidian Phallusia arabica was investigated against urinary tract infection bacterial pathogens using disc diffusion method. The crude ethyl acetate extract was more active exhibiting a broad-spectrum antibacterial activity than that of the crude methanol extract against each of the microbes tested. Maximum inhibition zone (12 mm) was observed against Proteus mirabilis in crude ethyl acetate extract (1 mg mL-1 concentration) and the minimum inhibition zone (1.5 mm) was observed against Pseudomonas aeruginosa in methanol extract (1 mg mL-1 concentration). The range of MICs and MBCs were high in ethyl acetate extract and it was low in the methanol extract. This result suggest that P. arabica can be used as effective inhibitor of urinary tract infection pathogens making them applicable to medical devices and antimicrobial control systems.