Background Antimicrobial resistance of Helicobacter pylori (H. pylori) affects the efficacy of eradication therapy. The aim of this study was to estimate the prevalence of primary and secondary resistance of H. pylori isolates to antibiotics and to characterize the risk factors associated with antimicrobial resistance in Korea. Materials and Methods This study was performed during the period of 2003–2012. Primary resistance was evaluated from 347 patients without any history of eradication, and secondary resistance was evaluated in 86 patients from whom H. pylori was cultured after failure of eradication. Minimal inhibitory concentration test was performed for amoxicillin, clarithromycin, metronidazole, tetracycline, azithromycin, levofloxacin, and moxifloxacin using agar dilution method. Primary and secondary resistance rates of H. pylori to 7 antibiotics were evaluated and risk factors for the antibiotic resistance were analyzed. Results Increase in the primary resistance rate was found in amoxicillin (6.3–14.9%, p = .051), clarithromycin (17.2–23.7%, p = .323), and both of levofloxacin and moxifloxacin (4.7–28.1%, p = .002) during the study period. Secondary resistance rate significantly increased in metronidazole, levofloxacin, and moxifloxacin. Increase of resistance occurred after initial failure of eradication therapy in case of clarithromycin (p
