Background <p><i>Klebsiella pneumoniae</i> exhibits a marked propensity for acquiring beta-lactam resistance genes. Among these, AmpC beta-lactamases are able to hydrolyze a broad spectrum of antibiotics including first- through third-generation cephalosporins, cephamycins, and aztreonam. The CIT, EBC, and DHA families are among the most clinically significant plasmid-mediated AmpC variants in this pathogen. Consequently, this study aimed to investigate the prevalence of genes encoding these specific enzymes among clinical isolates of <i>K. pneumoniae</i> in northern Iran.</p> Methods <p>One hundred clinical isolates were collected from hospitalized patients and identified using standard microbiological and biochemical assays. The antimicrobial resistance profile of each isolate was determined via the disk agar diffusion method. Subsequently, PCR test was employed to detect the presence of the <i>bla</i>_<i>CIT</i>, <i>bla</i>_<i>EBC</i>, and <i>bla</i>_<i>DHA</i> genes.</p> Results <p>The mean age of the patients (58 females and 42 males) was 50.31 years. Isolates were sourced from patients in general (41%), pediatric (45%), burn (7%), and infectious (7%) hospitals. The primary specimen sources were urine (64%), blood (10%), tissue (15%), wound (7%), and sputum (4%). The highest prevalence of resistance (93%) was observed against ampicillin-sulbactam, whereas 73% of isolates remained susceptible to ertapenem.</p> Conclusion <p>The high ampicillin-sulbactam resistance represents a serious concern for the management of hospital-acquired infections. Furthermore, while the presence of the investigated <i>bla</i>_<i>CIT</i>, <i>bla</i>_<i>EBC</i>, and <i>bla</i>_<i>DHA</i> genes did not show a statistically significant correlation with resistance to most tested antibiotics, their detection remains of potential clinical importance due to the risk of horizontal gene transfer to other bacterial species.</p>