Klebsiella pneumoniae is an opportunistic pathogen that commonly affects immunosuppressed patients and causes nosocomial infections. K.pneumoniae has a variety of virulence factors, especially capsule polysaccharide, hypermucoviscosity (HV), fimbriae, toxins and determinants for iron acquisition. The aim of this study was to detect the virulence factors in K.pneumoniae strains isolated from nosocomial infections in two years. Fifty three K.pneumoniae strains isolated from the samples of patients with nosocomial infections in the Medical Microbiology Laboratory of Selcuk University Faculty of Medicine Hospital between 2011 and 2013 were included in the study. Identification and antimicrobial susceptibilities of the isolates were performed by VITEK 2 automatic system. Biofilm formation,α-hemolysin, capsule and HV were investigated by phenotypic methods. Polymerase chain reaction (PCR) was used to detect virulence genes encoding adhesins (fimH-1, mrkD, kpn, ycfM), siderophores (entB: enterobactin, iutA: aerobactin, irp-1, irp-2, ybtS, fyuA: yersiniabactin, iroN: catechols receptor), protectines or invasins (rmpA, magA, traT) and toxins (hlyA, cnf-1). Of the 53 K.pneumoniae isolates,12 (22.6%) were isolated from in patients of reanimation intensive care unit, 8 (15.1%) medical oncology, 7 (13.2%) newborn intensive care unit and 26 (49%) other clinics. The distribution of the isolates according to the samples was as follows: urine (n= 14), blood (n= 13), wound (n= 8), drainage fluid (n= 10), broncho-alveolar lavage (n= 7), and cerebrospinal fluid (n= 1). Isolates which were resistant to meropenem were 5.7% and production of extended spectrum beta-lactamase (ESBL) was 71.7%. The capsule, biofilm formation, and HV were observed in 100%, 79.2%, and 1.9% of the isolates, respectively. Production of α-hemolysin was not detected in any of the isolates. The genes; entB (96.2%), ycfM (86.8%), and mrkD (83.0%) showed high prevalence. The other genes were detected in different ratios: fimH-1 (64.2%), fyuA (54.7%), kpn (49.1%), ybtS (41.5%), irp-1(41.5%), irp-2 (37.7%), traT (11.3%) and iutA (5.7%). Virulence genes; iroN, rmpA, magA, hlyA and cnf-1 were not detected in any of the isolates. Enterobactin had the highest rate among siderophores, and ycfM and mrkD in adhesins. The capsule and biofilm formation were commonly found in the isolates. Hypermucoviscosity was only found in one isolate but associated genes were not detected. Alfa hemolysin production and hlyA gene were not determined. As a result, it seems that the basis of the pathogenicity of K.pneumoniae strains isolated from nosocomial infections are capsule, adhesins, enterobactin and ability of biofilm formation. There is a need for new studies for the continuous monitoring of toxin and invasion ability as well as antibiotic resistance in the control of hospital infection caused by K.pneumoniae.