Carbapenem-resistant Acinetobacter baumannii (CRAB) is a major threat to public health and is a common cause of nosocomial outbreaks.To describe the genetic epidemiology of CRAB from both clinical and hospital environments in a network of hospitals in Hong Kong.A collection of 185 CRAB strains from patients (N = 143) and nosocomial environments (N = 42) for the period 2012-2024 underwent whole-genome sequencing to investigate the phylogenetic relatedness, virulence genes, and antibiotic resistance genes and possible lineages of the strains that caused nosocomial outbreaks. Clinical information and antibiotic susceptibility test reports were retrieved by electronic medical records. Time and spatial distribution of the strains were assessed.The dominant sequence type of CRAB was ST2, accounting for 137 of 185 isolates (74.1%). It was followed by ST195 (N = 17, 9.2%) and ST49 (N = 16, 8.6%). Dissemination of CRAB across time and space in the regional network of hospitals was observed. Environmental isolates possessed a greater number of genes encoding for virulence factors than human isolates (P