Klebsiella pneumoniae is one of the major bacteria that cause acute infections. β-lactamases are main defensive mechanisms in bacteria against drugs. The aim of this study was to determine antibiotic resistance patterns and detection of extended-spectrum-beta-lactamase (ESBL), MBL, Amp-C and KPC β-lactamases among K. pneumoniae strains isolated from adults and infants. This descriptive study was done on 83 K. pneumoniae isolated from two hospitals. Antibiotic susceptibility tests were performed by Kirby-Bauer disc diffusion and broth microdilution methods according to Clinical Laboratory Standards Institute (CLSI) guidelines. ESBLs, MBL, Amp-C and KPC producing strains were detected by phenotypic confirmatory test, combination disk diffusion test (CDDT), Amp-C detection kit and Modified Hodge test, respectively. From 83 K. pneumoniae strains, 48 (57.5%), 3 (3.5%), 23 (28%) and 5 (6%) were ESBL, MBL, Amp-C and KPC positive, respectively. In this study, Fosfomycin and Tigecycline were more active than other antibiotics. The results demonstrated that incidence of ESBLs, Amp-C, MBLs and KPC was critical especially in infants. Therefore, detection of drug resistance patterns in K. pneumoniae and β-lactamases producing isolates is important for the prevention and control of these infections.