Objective: To determine the antibiotic resistance patterns of the Acinetobacter (A.) baumannii complex isolates that cause the confirmed infection. Methods: The present descriptive study was performed from March 2016 to March 2018 in three referral hospitals in Isfahan, Iran. All A. baumannii complex strains isolated from different clinical samples were identified by conventional phenotypic methods and antibiotic susceptibility pattern was detected. After the clinical investigation, contaminated samples were excluded and the source (hospital/community) and site of the infection were determined. Data on antibiotic susceptibility testing were extracted from WHONET software and analysis was done with SPSS. Results: From 254 patients who had confirmed A. baumannii complex infection, 158 (62.20%) cases were male, 27 (10.63%) were less than 20 years old, 172 (67.72%) had healthcare-Associated infections and 96 (37.79%) were admitted in intensive care units. The most frequent infection was bloodstream infections (111, 43.70%). Our results showed that most of the isolates were resistant to most of the antibiotics (more than 75.00%) and a lower rate of non-susceptibility was observed against minocycline (20, 44.44%) and colistin (0%). The rate of multidrug-resistant isolates was 88.97%. There was no significant difference between resistance of A. baumannii complex isolates according to age. However, the resistance to amikacin and minocycline and the rate of multidrug resistance (MDR) were significantly different between males and females. In patients with healthcare associated infection (HAI), MDR isolates were significantly different regarding admission in ICU ward. Resistance to levofloxacin and ciprofloxacin were lower in isolates from patients with bloodstream infections in comparison to other diagnoses. Conclusions: In our study, a high level of antibiotic resistance was detected in both community-Acquired and healthcare-Associated A. baumannii complex infections. Appropriate antibiotic prescription in a clinical setting is an essential need for the control and prevention of A. baumannii resistant infections.