SIM-1 metallo-β-lactamase was first discovered from carbapenem-resistant Acinetobacter spp. isolated in a Korean University Hospital in 2003, and was recently reported to have been discovered in A. baylyi isolated in nearby China. The aims of this study were to reveal clonal changes in blaSIM-1-harboring Acinetobacter isolates collected from 2003 to 2008 in the same Korean hospital, where they were first discovered to gain further insight into the relation between blaSIM-1-harboring plasmids and Acinetobacter spp. Among 1,761 nonduplicated imipenem-resistant Acinetobacter spp. isolates, 29 isolates were identified as blaSIM-1 carriers. They were categorized into nine types according to pulsed-field gel electrophoresis findings. While most blaSIM-1-carrying isolates from 2003 to 2005 belonged to A. pittii, those from 2006 to 2007 were mostly isolates of A. nosocomialis. Most of the blaSIM-1 genes were carried on ca. 280-kb plasmids and were only discovered in non-baumannii Acinetobacter spp. Integrons carrying the blaSIM-1 gene were identical in structure in all species. These findings suggest that the plasmids were transferable, but not promiscuous. Further surveillance should be continued to detect and control further spread of the blaSIM-1 gene, as the appearance of the blaSIM-1 gene in different Acinetobacter spp. in different countries has already begun.