© 2015 Elsevier Ltd. Probiotics provide clinical benefit in a variety of gastrointestinal conditions, including inhibition of Helicobacter pylori (H. pylori). This study examined the effect of Bifidobacterium longum on H. pylori eradication in a randomized, double-blind placebo-controlled study. Dyspeptic patients with H. pylori infection were divided into two groups, treated with the standard triple therapy for 7 days and received B. longum or placebo for 4 weeks. Successful eradication therapy was defined as a negative 13C urea breath test 4 weeks after completion of the treatment. According to intention-to-treat analysis and per-protocol analysis, the infection was eradicated in 28/31 (90.32%), 28/30 (93.33%) from test group and in 22/32 (68.79%), 22/30 (73.33%) from control group, respectively, with significant differences. One (3.23%) patient in test group and eight (25%) patients in control group experienced diarrhea (P = 0.027). These results show the possibility that B. longum improves the H. pylori eradication and anti- H. pylori antibiotherapy-associated complications.