Objective To investigate and analyze the epidemiological characteristics and the causes of a suspected outbreak of carbapenem-resistant Acinetobacter baumannii (CRAB) infection, and provide basis for healthcare-associated infection (HAI) prevention and control. Methods Information of 3 patients with CRAB positive culture from the respiratory intensive care unit (RICU) of a hospital in May 2024 was collected. Microbiological sampling was performed in patients’ ward environment, and the specimens were cultured and strains were identified. CRAB strains detected from the environment and patients were performed whole genome sequencing (WGS). Multiple departments jointly formulated and implemented comprehensive infection control measures, and the effectiveness were evaluated. Results CRAB was cultured from specimens of sputum and bedside office mice of 3 patients. WGS detection showed that ST2158 and ST1791 resistance genes were detected from both sputum and bedside office mice of 2 patients. After comprehensive assessment, 2 patients were confirmed with HAI and 1 patient was confirmed with colonization, ruling out an outbreak of HAI. A total of 24 environmental specimens were taken for environmental hygiene monitoring, with a CRAB detection rate of 58.33%. CRAB detected from bedside mice and patients’ sputum specimen had consistent CRAB drug susceptibility testing results. After implementing measures such as increasing the frequency of cleaning and disinfection of ward environment, strengthening the implementation of hand hygiene, and enhancing the supervision of department personnel as well as HAI prevention and control training, HAI was effectively controlled. Conclusion The possible transmission route of this suspected CRAB outbreak in RICU is the contamination of office mice, which caused healthcare workers carrying CRAB in their hands, leading to cross infection due to poor hand hygiene implementation of healthcare workers. Strengthening the cleaning and disinfection of environmental surface and the management of hand hygiene of healthcare workers are key measures to prevent CRAB HAI.