Clustered, regularly interspaced short palindromic repeats (CRISPRs) and their related genes (Cas) are prevalent in the genomes of several bacteria and serve as a defense mechanism against external attackers, such as plasmids and viruses. This study aimed to examine the frequency of the CRISPR/Cas system in naturally occurring strains of Klebsiella pneumoniae sub spp pneumoniae confirmed by Vitek 2 biochemical test, in the hospital setting and determine its correlation with antibiotic resistance both phenotypically and genetically (antibiotic-resistant genes, namely blaTEM and AcrA efflux pump gene). The research was conducted at Medical College/ Mosul University 23 multi-drug resistant K. pneumoniae sub spp. pneumoniae that were obtained from 230 clinical samples from infected patients with different types of infections attending Al-Salam and Al-Jumhoree Teaching hospitals. PCR was used to detect blaTEM, AcrA genes, and CRISPR/Cas system genes (CAS1A and CAS1B) among the clinical isolates. The correlation between the CRISPR/Cas system and antibiotic-resistance was determined. All the isolates were multiple drug-resistant strains, and the blaTEM gene was detected in all clinical isolates, whereas AcrA gene was detected in 94% of the isolates. The frequency of CAS1A and CAS1B was 21.73% and 86.95% respectively. There was an inverse correlation between the CAS1A gene and phenotypic antibiotic resistance Disc diffusion test results, so isolates carrying CAS1A gene were less resistant to different antibiotics studied in this research. In contrast, there was no significant correlation between CRISPR / Cas genes, blaTEM, and AcrA genes at the genetic level.