Here we present the characteristics of a large outbreak caused by a clonal Klebsiella pneumoniae strain producing both KPC-2 and VIM-1 carbapenemases in a tertiary teaching hospital. Between January 2013 and January 2015, 45 carbapenem-resistant K. pneumoniae isolates that gave a positive modified Hodge test and were phenotypically suspected of metallo-β-lactamase (MBL) and K. pneumoniae carbapenemase (KPC) co-production were recovered from 25 patients hospitalised in AHEPA University Hospital (Thessaloniki, Greece). All of the patients were hospitalised in the three intensive care units of the hospital and 17 (68%) of them developed bloodstream infections; the overall mortality of the patients involved in the outbreak was 48% (12/25). Molecular testing verified that all 45 K. pneumoniae isolates co-harboured bla_KPC-2 and bla_VIM-1 genes and were associated with OmpK35 deficiency and OmpK36 porin loss. The bla_TEM-1 gene was also present in 18 isolates. Pulsed-field gel electrophoresis (PFGE) clustered all of the isolates into a single clonal type, and multilocus sequence typing (MLST) assigned them to the emerging high-risk ST147 clonal lineage. Following recognition of the outbreak, infection control measures were implemented in the affected areas. The outbreak continued for ca. 2 years and since then only sporadic cases of K. pneumoniae harbouring both carbapenemases have been detected.