Background: Irritable bowel syndrome (IBS) is a common functional bowel disorder characterized by recurrent abdominal pain or discomfort associated with altered bowel habit. Recent studies have shown that vitamin D can influence numerous pathways involved in the development of IBS. The actual pathophysiologic processes involving IBS patients are still unknown.  The aim of this study is to assess vitamin D level in patients with irritable bowel syndrome and estimate whether there is correlation between serum level of vitamin D and IBS. Methods: total of 113 people was studied, 45 subjects who diagnosed as irritable bowel syndrome according to ROME IV criteria, 23 met the exclusion criteria and 45 healthy subjects as a control group. Blood sample was taken to measure vitamin D in serum (25-hydroxyvitamin D) Results: vitamin D deficiency was found to be higher in the IBS group (76.6%) compared to control group (46.7%). When different subtypes were analyzed IBS-C subtype (62.2%) was more common than IBS-D subtype (20%) and IBS-M subtype (17.8%). Conclusion: Vitamin D, which plays a role in inflammatory processes, may also be of relevance in the pathophysiology of IBS. Vitamin D plays a crucial role in intestinal health by strengthening the mucosal barrier, regulating immune responses, and acting as an antimicrobial itself. In this study we found that vitamin D deficiency was found to be higher in the IBS group, so there is relation between vitamin d deficiency and irritable bowel syndrome.