We investigated the genetic properties of two carbapenem-resistant Pseudomonas aeruginosa isolates collected from a regional hospital in the north of Thailand. Both isolates demonstrated high-level resistance to extended-spectrum cephalosporins and carbapenems. Detection of the MBL genes was positive for bla (IMP) in both isolates. Pulsed field gel electrophoresis (PFGE) analysis showed that the two P. aeruginosa isolates were nonclonal. Molecular analysis of the bla (IMP) in isolate 837 showed the presence of a bla (IMP-1) gene inserted in a class 1 integron. The bla (IMP-1) was plasmid-mediated according to the transformation assay. This is the first case of the bla (IMP-1) gene in carbapenem-resistant P. aeruginosa in Thailand, suggesting the further dissemination of this gene in Southeast Asia.