The spread of multi-drug resistant (MDR) Gram-negative bacteria, including Klebsiella pneumoniae, constitutes a global threat. The most frequent mechanism of acquired carbapenem resistance is the production of carbapenemases, especially KPC, NDM, VIM, IMP and OXA-48. We analyzed the epidemiological trend of carbapenem resistance genes of carbapenem-resistant K. pneumoniae (CRKP) strains isolated from critically ill patients in a Greek tertiary hospital. The study included 150 CRKP isolates collected from 116 (77.4%) patients hospitalized in the adult ICU and 17 (11.3%) each in the pediatric and the two neonatal ICUs between March 2018 and March 2021. Identification and antimicrobial susceptibility testing were performed using VITEK-2. A multiplex lateral flow immunoassay was used for the detection of carbapenemases, while the detection of blaVIM, blaKPC, blaNDM, blaIMP and blaOXA-48-like genes was achieved by multiplex PCR. The blaNDM was mainly detected in adults (54/116, 46.9%), while in children the most often detected gene was blaKPC (24/34, 70.6%). The predominant carbapenem resistance gene during 20182019 was blaKPC alone or in combination with blaVIM, reaching 44.4% in 2019, while during 2020-2021 the detection of blaNDM prevailed significantly, reaching 45.5 and 60.7% for 2020 and 2021, respectively. A shift in the molecular epidemiology of CRKP was seen during 2018-2021, which is probably associated with the recent excessive empiric use of newer antimicrobials. Surveillance studies and proper and strict implementation of infection control measures are highly needed to decrease the spread of MDR bacteria, including CRKP.  Kulcsszavak: Klebsiella pneumoniae, carbapenem-resistant, intensive care unit, Greece