Background: Although current standard first-line treatment to eradicate Helicobacter pylori is triple therapy combining a proton pump inhibitor with two antibiotics (mainly clarithromycin and amoxicillin or metronidazole), there is increasing tendency to alter this treatment. Cure rates with first-line 14-day triple therapy in the geographic area including our country can barely reach 45-50%. Modification of standard first-line treatment by adding bismuth subcitrate has been suggested to increase this relatively low cure rates. Aim: The aim of this study was to assess efficacy of adding product containing several probiotic strains as an adjuvant to modified first-line treatment to eradicate H.pylori. Materials and Methods: An open label observational clinical study was designed to compare two patient groups receiving modified triple therapy and bismuth subcitrate (Group 1, n=100) with a regimen consisting of modified triple therapy and bismuth subcitrate plus concomitant NBL probiotic added at the same time (Group 2, n=150). In Group 1, patients were given a 14-day treatment program consisting of lansoprazole 40 mg (b.i.d.), amoxicillin 1 gr (b.i.d.), clarithyromycin 500 mg (b.i.d) and colloidal bismuth subcitrate 300 mg (2 tablets before breakfast and dinner). In Group 2, NBL probiotic (active probiotics: Lactobacillus acidophilus, Enterococcus faecium, Lactobacillus plantarum, Bfidobacterium lactis, Streptococus thermophilus, Bfidobacterium longum, 1.5 x 109 cfu/chewable tablet) tablets (b.i.d) for 14 days was given in addition to the same modified first-line treatment used for Group 1. Eradication was tested by urea breath test (UBT) 6 weeks after completion of treatment. Results: In Group 1, 89 patients were available for follow up and 69 patients eradicated H.pylori. In Group 2, 134 patients were available for follow up and 120 patients eradicated H.pylori. Per protocol and intention to treat eradication rates were 77.5% and 69.0%, respectively for Group1 and were 89.6% and 80,0% respectively for Group 2. Adding NBL probiotic to triple therapy and bismuth subcitrate has led to a statistically significant more successful eradication rates in both PP and ITT analyses (x2 test: P <0.05 and P<0.05). Conclusion: Contradicting results have been reported in previous studies about the effects of probotics in H.pylori eradication. Our results suggest that adding products containing probiotic strains as an adjuvant to modified first-line therapeutic regimen used for eradication of H. pylori infection significantly improves the cure rates.