Carbapenems are broad-spectrum antibiotics that are losing effectiveness against infections caused by multidrug-resistant Enterobacterales that have acquired carbapenemase genes. The New Delhi metallo-β-lactamase (bla NDM) is one of the most common carbapenemases in Canada and around the globe. These genes are frequently found on conjugative plasmids, which can disseminate through horizontal gene transfer. We applied whole-genome sequencing to characterize 1,032 bla NDM carbapenemase-producing Enterobacterales isolates collected by the Canadian Nosocomial Infection Surveillance Program from 2010 to 2023. Using a combination of short-read and long-read sequencing, we obtained 226 complete and circular bla NDM-encoding plasmids. Unlike other carbapenemases in Canada, we found that bla NDM plasmids were very diverse; there was a lack of dominant clusters identified using MOB-suite, and clustering methods were not able to accurately predict plasmid clusters for short-read-only data. The majority of bla NDM plasmids were IncF-type (69.0%, 156/226). Both bla NDM and bla OXA-48-type carbapenemase genes were found in 11.4% (118/1,032) of isolates, and we identified several instances of both carbapenemase genes co-harboured on the same plasmid replicon (n=9). Our findings highlight that plasmid transfer has not played a major role in bla NDM transmission across Canada and that long-read sequencing is essential for resolving bla NDM plasmid structure and cluster membership.