Objectives To investigate the β-lactamase background of ertapenem non-susceptible isolates for the presence of the most commonly detected carbapenemase genes, bla KPC, bla OXA-48 and bla VIM, and the newly described bla NDM-1. Methods Two hundred and thirty-five ertapenem-non-susceptible (MIC ≥0.5 mg/L) isolates of Enterobacteriaceae from the worldwide Study for Monitoring Antimicrobial Resistance Trends (SMART) 2009 programme were screened using a multiplex PCR for the presence of bla KPC, bla OXA-48, bla VIM and bla NDM-1 genes. Extended-spectrum β-lactamase (ESBL) and AmpC genes (bla ESBL and bla AmpC) were identified using the Check-MDR CT101 microarray. DNA sequencing was performed to identify the bla ESBL, bla KPC and bla NDM-1 genes. Molecular typing was also performed to genetically characterize these isolates. Results Sixty-six isolates (28%) had a carbapenemase gene, with bla NDM-1 identified in 33 isolates including 2 isolates carrying both bla NDM-1 and bla OXA-48; other carbapenemase genes found included bla KPC (n = 23), bla VIM (n = 7) and bla OXA-48 (n = 3). All bla NDM-1-carrying isolates were from patients in India and comprised five different species. With the exception of one isolate carrying only bla NDM-1, all bla NDM-1 carbapenemase-possessing isolates carried additional β-lactamases in various combinations: bla ESBL and bla AmpC (n = 18); bla ESBL (n = 10); bla ESBL, bla AmpC and bla OXA-48 (n = 2); and bla AmpC (n = 2). Except for bla OXA-48-carrying isolates, novel multilocus sequence types or enterobacterial repetitive intergenic consensus PCR patterns were observed along with clonal dissemination within and among sites. Conclusions A range of carbapenemase genes, associated with diverse ESBLs and/or AmpC backgrounds, were found among Enterobacteriaceae isolated during the study. Many of these ertapenem non-susceptible strains were clonally related and carried various combinations of β-lactamases.