Background:The hospital environment usually involves in cross-colonization and/or outbreaks of carbapenem-resistant Acinetobacter baumannii (CRAB). This study aims to identify genetic diversity of environmental Acinetobacter baumannii (A. baumannii) isolates based on OXA-type carbapenems. Objectives: It was intended to identify the environmental source of A. baumannii strains to control future infections and ongoing outbreaks. Methods: Swab samples were collected from equipment, fluids and surfaces of intensive care units of five hospitals (H1 to H5). The susceptibility of the isolates was defined through disk diffusion method. blaOXA-51, blaOXA-58, blaOXA-23, and blaOXA-24 genes were detected by multiplex polymerase chain reaction (PCR) . Genetic diversity was investigated using ERIC-PCR. Mean values were compared using an Independent samples t-test. Results:The mean number of Gram-negative bacilli colony per sample was significantly higher in moist surfaces (1.9 ± 2.37) than in dry surfaces and medical equipment (P < 0.05). Among 32 A. baumannii isolates, 17 (53.1%) were classified as CRAB, 13 (40.6%) as multidrug resistant (MDR) and six (18.8%) as extremely drug resistant (XDR) phenotypes. The isolates showed the most susceptibility to tigecycline (81.3%) and doxycycline (81.3%). Totally, 10 isolates (31.3%) carried blaOXA-23 and one isolate carried blaOXA-58, but none contained blaOXA-24. Typing of the strains provided seven single types (ST) and nine clusters (A-I). Two isolates in cluster B (different surfaces of H4) and two in cluster I (from ventilators of H3 and H1) were designated as common type (CT). In H4 and H1, different isolates belonging to different clusters were recovered from bed sheet and baby sink bath, respectively. Conclusions: Clonally-related blaOXA-23 positive CRABs occurred in the environment, especially on moist surfaces of hospitals. The distribution of the same clones in different hospitals may point to expansion of a specific clone which increases the risk of crosscolonization of vulnerable patients.