Background: Irritable bowel syndrome (IBS) is considered one of the most common functional gastrointestinal disorders. The pathogenesis of IBS is still unknown, as it has both physiological and psychological factors. Being a multifactorial disorder, the treatment of IBS is thereby challenging and also conflicting. Conventional therapy might have an effect in mild and recently diagnosed cases but for some while and some extent. So, antidepressant medications were proposed to treat IBS with long lasting effect. This study aimed to compare effect of sertraline to placebo in treatment of IBS and its comorbid anxiety and/or depressive symptoms.