Pseudomonas aeruginosa is an opportunistic pathogen that colonizes urinary catheters, forms biofilms, and is responsible for causing persistent and recurrent nosocomial catheter-associated urinary tract infections (UTIs). These infections show increased morbidity and mortality in immunocompromised patients. Quorum sensing in P. aeruginosa plays a key role in biofilm formation, virulence factor production and antimicrobial resistance. Because of emerging antimicrobial resistance in P. aeruginosa, there is a need to find an alternate nonantibiotic agent for the control of infections caused by this organism. In the present study, garlic was evaluated as a prophylactic agent in vivo in a mouse UTI model. Oral treatment with garlic significantly lowered renal bacterial counts and protected mouse kidney from tissue destruction. In vitro data showed decreased elaboration of virulence factors and reduced production of quorum-sensing signals by P. aeruginosa in the presence of fresh garlic extract. The results suggest that decreased virulence of P. aeruginosa in garlic-fed mice can be attributed to the quorum-sensing inhibitory property of garlic. This might have contributed towards reduced production of virulence factors, as seen in vitro.