Levofloxacin is an effective medication for second line Helicobacter pylori (H. pylori) eradication. However, limited studies have approved its use as an effective antibiotic in first line therapy. Dexlansoprazole is a new PPI and lacks of evidence in support of a role in H. pylori eradication. This study was designed to evaluate efficacy of levofloxacin-dexlansoprazole-based quadruple therapy for H. pylori eradication in Thailand. This prospective randomized control study was performed during June 2014 to December 2014. H. pylori infected gastritis patients were randomized to receive 7- or 14-day levofloxacin-dexlansoprazole based on quadruple therapy (levofloxacin 500 mg OD, dexlansoprazole 60 mg bid, clarithromycin MR 1000 mg OD, bismuth subsalicylate 1048 mg bid). CYP2C19 genotyping and antibiotic susceptibility tests were conducted for all patients. A 13C urea breath test was performed to confirm H. pylori eradication at least 4 weeks after treatment. A total of 100 patients were enrolled, comprising 44 males and 56 females (mean age of 52.6 years). Eradication rate by PP analysis was 85.7% (42/49) with the 7-day regimen and 98% (48/49) with the 14-day regimen (85.7% vs 98%; p-value=0.059). ITT analysis was 84% and 96% with 7- and 14-day regimens, respectively (84% vs 96%; p-value=0.092). Antibiotic susceptibility testing demonstrated 35.1% resistance to metronidazole, 18.3% to clarithromycin, and 13.5% to levofloxacin. CYP2C19 genotyping revealed 54.1% RM, 34.7% IM and 11.2% PM. The 14-day regimen provided 100% eradication in patients with clarithromycin or dual clarithromycin and metronidazole H. pylori resistant strains. Moreover, the eradication rate was 96.6% in patients with CYP2C19 genotype RM. The 14-day levofloxacin-dexlansoprazole based quadruple therapy provides high H. pylori eradication regardless of CYP2C19 genotype, clarithromycin or dual clarithromycin and metronidazole resistant strains. This regimen could be use as an alternative first line therapy for H. pylori eradication in Thailand.