Multilocus sequence typing and in vitro antimicrobial susceptibility testing were performed for three community-onset New Delhi metallo-β-lactamase-1 (NDM-1)-producing Klebsiella pneumoniae isolates from Korea. The genetic structure surrounding the bla _NDM-1 gene was determined in bla _NDM-1-harbouring plasmids. Three NDM-1-producing K. pneumoniae isolates were found to belong to the same clone (sequence type 340). Each of these isolates showed the same genetic structure surrounding the bla _NDM-1 gene. The genes bla _NDM-1, ble _MBL, trpF and dsbC were flanked by two intact insertion sequences, ISAba125 and IS26, which may promote horizontal gene transfer. The bla _NDM-1-harbouring plasmids conferred antimicrobial resistance to carbapenems, cephalosporins, aminoglycosides and aztreonam in transconjugants. It can be speculated that either the entire bla _NDM-1-harbouring plasmids or just the part of the plasmid containing the bla _NDM-1 gene may have transferred between K. pneumoniae and Escherichia coli. Following the transfer, the isolate disseminated throughout Korea. This study suggests the need for monitoring the dissemination of NDM-1-producing isolates across countries or continents due to their potential transferability via ISAba125- and IS26-associated transposons.