Background: Pseudomonas aeruginosa (P. aeruginosa) is an opportunistic pathogen that represents a major problem in many hospitals because of its increased resistance to antibiotics and the ability to cause nosocomial infections. The present study aimed to phenotype and genotype isolates of P. aeruginosa from inpatients with UTIs at Urology and Nephrology center, Mansoura, Egypt to study their relatedness. Methods: Thirty nine isolates of P. aeruginosa were phenotypically typed by determination of O-serotypes by slide agglutination technique and antimicrobial resistance patterns by disk-diffusion method. The genetic diversity of isolates was illustrated by performing RAPD-PCR using M13 primer. Results: Serotypes O11, O6 and O10 were the most prevalent. Isolates showed high resistance rates to antipseudmonal antibiotics with high incidence (51.3%) of multidrug resistance (MDR). Amikacin was the most effective. A significant correlation was found between O6, O10 and MDR. A relatively high polymorphism was demonstrated among P. aeruginosa isolates by using RAPD-M13 fingerprinting. Cross transmission was suggested by phenotypically and clonally identical isolates. Conclusion: The study demonstrates the role of combining both classical and molecular typing as a valuable mean to study the origin and cross transmission of P. aeruginosa in UTIs for better assessment of treatment and infection control.