Helicobacter pylori is a gram-negative bacterium that is present in almost half of the population. Recent studies have shown a positive correlation between H. pylori infection and migraine headache. The aim of this study was to asses the impact of H. pylori eradication on migraine headache. This randomized clinical trial study carried out on 108 patients with migraine without aura, who were admitted in neurology clinics in a university affiliated hospital. Patients randomly were divided into two groups. The first group underwent eradication of H. pylori infection with a three drug regimens. H.pylori infection confirmed by Urease Breathing Test. Patients in the second group received only migraine treatment. One month after completion of therapy was repeated to assess eradication of infection. The number and severity of attacks in both groups before treatment, second and fourth months after eradication was measured. Eradication of H. pylori was successful in 47 patients. In treatment group score of attacks during 2th (p<0.001) and 4th months after eradication were significantly decreased (p<0.001). Also, such decrease was observed in the control group (n=61). Migraine score change in the two groups after 2 months of eradication was significantly different (p= 0.049). But 4 months after eradication, there was no significant difference between the two groups (p = 0.082). According to our study, clinical manifestation of migraine improves two months after H. pylori eradication but four months after eradication. Eradication of this infection can be effective in decreasing severity of the migraine attacks.