Background: Pseudomonas aeruginosa (P. aeruginosa) is an opportunistic pathogen that is a leading cause of many types of infections both healthcare associated infections (HAIs) or community acquired infections. In general, this organism is highly resistant to different classes of antimicrobials through different mechanisms that represents a major concern in treatment of infections in hospitals. Aim of the study: To detect the association between the presence of MexA/MexB genes and the resistance pattern among P. aeruginosa. isolates from Ain Shams University Hospitals. Methods: A total of 60 isolates of P. aeruginosa were obtained from Main Microbiology Laboratory, Ain Shams University Hospitals. Phenotypic identification and antimicrobial susceptibility testing were performed followed by detection of MexA/MexB genes using polymerase chain reaction (PCR). Results: Most of isolates were isolated from urine samples 26 (43.3%), followed by sputum samples 14 (23.3%). Antimicrobial susceptibility showed highest maximum resistance to cefepime (97%), ceftazidime (90%), gentamycin (87%), Piperacillin (73%) and ciprofloxacin (60%). The least resistance was reported to meropenem (63%), imipenem (60%) and piperacillin/tazobactam (43%). 38 (63.3%) isolates were extensive drug resistance (XDR), 12 (20%) isolates were multi-drug resistance (MDR) and 10 (16.7%) isolates were non-MDR. MexA and mexB genes were detected in 56.7% (34 strains) and 46.7% (28 strains) of all tested isolates, respectively. According to our results, all strains that carry mexB gene carry MexA gene as well. Conclusion: Antimicrobial resistance amongP. aeruginosa is widely spreadingand significantly associated with presence of MexA/MexB gene.