Two hundred fifty Klebsiella pneumoniae isolates were collected during October 2013 to February 2014 from two different tertiary hospitals in Riyadh, Saudi Arabia. Eighty out of 250 isolates K. pneumoniae were selected according to reduced susceptibility to extended-spectrum cephalosporins (ESC). Phenotypic tests for extended-spectrum b-lactamases (ESBLs), carbapenemases, and AmpC enzyme-producing isolates were performed to detect the resistance phenotype of the isolates. The antimicrobial susceptibility testing was done. The whole collection was found to be tigecycline, colistin and fosfomycin sensitive. The resistance rates to amoxicillin, amoxicillin/clavulanic acid, piperacillin, piperacillin/tazobactam, ceftazidime, cefotaxime, ceftriaxone, cefoxitin, imipenem, amikacin, ciprofloxacin, sulphamethoxazole/trimethoprim, tetracycline were 100%, 95%, 90%, 48.75%, 77.5%, 86.25%, 86.25%, 55%, 3.75%, 7.5%, 70%, 88.75%,  and 83.60%, respectively. ESBLs, and carbapenemase, and AmpC production were seen in 80%, 25% and 13.75% of ESC insensitive K. pneumoniae isolates, respectively. The prevalence of metallo- and non-metallo carbapenemase producing K. pneumoniae isolates were 8.75% (n= 7/80) and 17.5% (n=14/80), respectively. All carbapenemase producers were also found to be ESBLs positive and/or AmpC positive. Our study documented the high rate of antibiotic resistances and high prevalences of ESBLs, AmpC and carbapenemases in K. pneumoniae isolates.