The aim of this study was to identify risk factors for mortality in patients suffering from hematological malignancies (HMs) with bloodstream infections (BSIs) caused by Klebsiella pneumoniae (KP). We conducted a prospective cohort study on KP BSI in 13 Italian hematological units participating in the HEMABIS registry–SEIFEM group. The outcome measured was death within 21 days of BSI onset. Survivor and non-survivor subgroups were compared and Cox regression analysis was conducted to identify independent predictors of mortality. A total of 278 episodes of KP BSI were included in the study between January 2010 and June 2014. We found that 161 (57.9%) KP isolates were carbapenem resistant (CRKP). The overall 21-day mortality rate was 36.3%. It was significantly higher for patients with CRKP BSI (84/161, 52.2%) than for those with BSI caused by carbapenem susceptible KP (CSKP) (17/117, 14.5%; P < 0.001). Septic shock (HR 3.86), acute respiratory failure (HR 2.32), inadequate initial antimicrobial therapy (HR 1.87) and carbapenem resistance by KP isolates (HR 1.85) were independently associated with mortality. A subanalysis was conducted in only 149 patients with CRKP BSI who had received ≥48 hr of adequate antibiotic therapy, and combination therapy was independently associated with survival (HR 0.32). Our study shows that in recent years carbapenem resistance has dramatically increased in HM patients with KP BSI in Italy and is associated with a worse outcome. The optimal management of such infections and the definition of new empirical/targeted antimicrobial strategies in HM patients can still be considered unmet clinical needs. Am. J. Hematol. 91:1076–1081, 2016. © 2016 Wiley Periodicals, Inc.