Irritable bowel syndrome (IBS) is one of the common and chronic functional gastrointestinal disorders that cause a great burden for the patients and the society. Therefore, investigation of psychological variables related to IBS can be useful in understanding, management and decrees of symptoms severity in IBS patients. The present study was performed to examine the mediating role of alexithymia on the relationship between early maladaptive schemas and severity of symptoms in patients with irritable bowel syndrome. One hundred and eighty patients with irritable bowel syndrome (114 men, 66 women) participated in this study. All patients were asked to complete the IBS symptom severity scale (IBS-SSS), young schema questionnaire-short form (YSQ-SF), and Toronto Alexithymia scale (TAS-20). The results demonstrated that early maladaptive schemas and alexithymia had a significant positive association with severity of IBS symptoms )p<0.05). Also early maladaptive schemas had a significant positive association with alexithymia )p<0.01). The results showed that alexithymia did not play a mediating role on the relationship between early maladaptive schemas and IBS severity of symptoms. According to the results of the present study, it can be concluded that early maladaptive schemas and alexithymia can predict severity of IBS symptoms. Considering these psychological variables would be helpful in the processes of prevention, diagnosis and treatment of IBS