Carbapenem resistantPseudomonas aeruginosawere isolated among multidrug-resistant (CR-MDR) organisms from tertiary hospitals in Thailand. Decreased expression ofoprDmRNA (93.65%) was predominant followed by increased expression ofmexAB-oprMmRNA (92.06%) andmexXYmRNA (63.49%). Interestingly, 23 of 126 (18.25%) isolates were susceptible to imipenem with down-regulatedoprDexpression and non-up-regulatedmexCD-oprJmRNA expression. Metallo-β-lactamases production was clearly positive in 24 isolates (18.46%) and weakly positive in 12 isolates (9.23%). Among both of these sets of isolates,imp-1,imp-14andvim-2were identified. Hyperproduction of AmpC β-lactamase had the lowest prevalence rate (3.97%). It was concluded that CR-MDRP. aeruginosaclinical isolates in Thailand possess multifactorial resistance mechanisms.