ABSTRACTKlebsiella pneumoniaeproduces several kinds of bacteriocins that have antimicrobial effects against closely related species, but few studies have comprehensively reported bacteriocin distribution among theKlebsiellapopulation. In this study, we identified bacteriocin genes in 180K. pneumoniaespecies complex genomes, including 170 hypermucoviscous isolates, and investigated the antibacterial activity against 50 strains, including antimicrobial-resistant organisms, belonging to multiple species, namely,Klebsiellaspp.,Escherichia coli,Pseudomonasspp.,Acinetobacterspp.,Enterobacter cloacae,Stenotrophomonas maltophilia,Chryseobacterium indologenes,Staphylococcus aureus,Staphylococcus epidermidis, andStreptococcus mutans. Our study determined that 32.8% (59/180) of isolates carried at least one bacteriocin type. Different types of bacteriocin were usually present in different specific sequence types (STs); meanwhile, bacteriocins were not detected in certain STs. Microcin E492 was the most prevalent bacteriocin (14.4%), mostly in ST23 isolates, and displayed a wide spectrum of activity, including againstKlebsiellaspp.,E. coli,Pseudomonasspp., andAcinetobacterspp. Cloacin-like bacteriocin was detected in 7.2% of strains, all of which were non-ST23 isolates, and exhibited inhibitory activity against closely related species, mainlyKlebsiellaspp. Klebicin B-like bacteriocin was detected at a rate of 9.4%, although 82.4% of these strains carried a disrupted bacteriocin gene, and an inhibitory effect could not be observed from the intact-gene-carrying isolates. Other bacteriocins, such as microcin S-like, microcin B17, and klebicin C-like, were detected at lower rates and had limited inhibitory activity. Our findings suggested thatKlebsiellastrains that carry different bacteriocin types may affect the composition of the surrounding bacterial community.IMPORTANCEKlebsiella pneumoniaeis a Gram-negative commensal bacterium that asymptomatically colonizes human mucosal membranes, such as the intestinal tract, but it is also a leading cause of health care- and community-associated infections. Additionally, multidrug-resistantK. pneumoniaehas been continuously evolving, which significantly challenges the available chemotherapeutic treatment for its infections.K. pneumoniaeproduces several kinds of antimicrobial peptides known as bacteriocins, which have antibacterial activity against closely related species. This work was the first comprehensive report of bacteriocin distribution among the hypermucoviscousK. pneumoniaespecies complex population and the inhibitory activity of each bacteriocin type against various species, including multidrug-resistant strains. Our findings provide a foundation for future studies on theK. pneumoniaespecies complex, including studies on the competition within the microflora and the potential applications of bacteriocins in treating multidrug-resistant bacteria.