Despite the growing importance of carbapenem-resistant Klebsiella pneumoniae (CRKP), the clonal relationships between CRKP and antibiotic-susceptible isolates remain unclear. We compared the genetic diversity and clinical features of CRKP, third-generation and/or fourth-generation cephalosporin-resistant (Ceph-R) K. pneumoniae, and susceptible K. pneumoniae isolates causing bloodstream infections at a tertiary care hospital in New York City between January 2012 and July 2013. Drug susceptibilities were determined with the Vitek 2 system. Isolates underwent multilocus sequence typing and PCR sequencing of the wzi and bla _KPC genes. Clinical and microbiological data were extracted from patient records and correlated with molecular data. Among 223 patients, we identified 272 isolates. Of these, 194 were susceptible, 30 Ceph-R, and 48 CRKP, belonging to 144 sequence types (STs). Susceptible (127 STs) and Ceph-R (20 STs) isolates were highly diverse. ST258 dominated CRKP strains (12 STs, with 63% ST258). There was minimal overlap in STs between resistance groups. The bla _KPC-3 gene (30%) was restricted to ST258/wzi154, whereas bla _KPC-2 (70%) was observed for several wzi allele types. CRKP infections occurred more frequently among solid organ transplant (31%) and dialysis (17%) patients. Mortality rates were high overall (28%) and highest among CRKP-infected patients (59%). In multivariable analyses, advanced age, comorbidities, and disease severity were significant predictors of 30-day mortality rates, whereas the K. pneumoniae susceptibility phenotype was not. Among CRKP infections, we observed a borderline significant association of increased mortality rates with ST258 and the wzi154 allele. Although the clonal spread of ST258 continues to contribute substantially to the dissemination of CRKP, non-ST258 strains appear to be evolving. Further investigations into the mechanisms promoting CRKP diversification and the effects of clonal backgrounds on outcomes are warranted.