The efficacy of sequential therapy and the applicability of genotypic resistance to guide the selection of antibiotics in the third-line treatment of Helicobacter pylori have not been reported. We aimed to assess the efficacy of genotypic resistance-guided sequential therapy in third-line treatment. Genotypic and phenotypic resistances were determined in patients who failed at least two eradication therapies by PCR with direct sequencing and agar dilution test, respectively. The patients were retreated with sequential therapy containing esomeprazole and amoxicillin for the first 7 days, followed by esomeprazole and metronidazole plus clarithromycin, levofloxacin or tetracycline for another 7 days (all twice daily), according to genotypic resistance determined using gastric biopsy specimens. Eradication status was determined by the C-13-urea breath test. Trial registered at clinicaltrials.gov (identifier: NCT01032655). The overall eradication rate was 80.7 (109/135, 95 CI 73.386.5) in the intention-to-treat analysis. The presence of amoxicillin resistance (OR 6.83, 95 CI 1.6228.86, P0.009) and prior sequential therapy (OR 4.77, 95 CI 1.31517.3, P0.017), but not tetracycline resistance (tetracycline group), were associated with treatment failure. The eradication rates in patients who received clarithromycin-, levofloxacin- and tetracycline-based sequential therapies were 78.9 (15/19), 92.2 (47/51) and 71.4 (25/35) in strains susceptible to clarithromycin, levofloxacin and tetracycline, respectively. A simple molecular method guiding sequential therapy can achieve a high eradication rate in the third-line treatment of refractory H. pylori infection.