Objective: Acinetobacter baumannii is among the most common bacterial agents causing nosocomial infections in the world. In recent years, the antibiotic resistance of A. baumannii strains has shown an increasing trend, which may be resulted from the activity of efflux pumps. This study was carried out to determine the efflux pump genes associated with MDR in clinical isolates of A. baumannii in Tehran province.Methods: In this study, 200 clinical samples were collected, and were identified through standard biochemical tests. Then, for the selected antibiotics, the antibacterial susceptibility patterns were determined using disk diffusion method with and without inhibitors of efflux pumps of adeJ, adeH, adeB, adeG, adeF, and adeS that were determined by employing PCR according to the Clinical & Laboratory Standards Institute (CLSI 2020) guideline.Results: A total of 60 clinical isolates of A. baumannii were identified and later confirmed by the detection of blaOXA-51-like and 16S rRNA genes. The findings of this study show that 98.37% of A. baumannii isolates were 100% resistant against piperacillin, meropenem, cefotaxime, ceftriaxone, ceftazidime, ceftazidime, and ciprofloxacin. In addition, 100% of all A. baumannii isolates possessed AdeFBJ, 95% adeH, 80% adeS, and 76.7% adeG efflux pumps. Conclusion:The majority of A. baumannii isolates had antibiotic efflux pumps, and more than 73% of A. baumannii isolates were indicated to be resistant to the target antibiotics, indicating the significant role of efflux pumps in the development of resistance against these antibiotics.