Irritable bowel syndrome (IBS) is a common GI functional disorder, which presents with a wide range of symptoms such as chronic abdominal discomfort, bloating and altered bowel habits. The variety of symptoms has led to a difficult therapeutic challenge and no specific treatment for relieving all IBS symptoms has been suggested yet. The purpose of this study was to evaluate the impact of Chamomile extract on IBS symptoms. In a randomized trial, 45 patients who fulfilled the ROOM III criteria and had no organic disease enrolled in this study and were asked to take Chamomile 20 drops daily for four weeks. They were asked to fill in IBS-associated symptoms questionnaire to specify abdominal pain intensity, bloating, nausea, stool consistency and altered bowel habits. The questionnaire was filled out during 5visits: at the first day, at the second and fourth weeks after starting the treatment and also the second and fourth weeks after the end of intervention. IBS symptoms were significantly reduced at the second and fourth weeks after beginning of the herbal therapy (p<0.001). Symptom relief continued up to 2 weeks after the end of intervention and started to decrease in 4 weeks after beginning of the herbal therapy. Considering the improving effects of Chamomile on all IBS symptoms, it may have a positive effect on the syndrome pathogenesis as well.