Objective: To quantify the prevalence of Irritable Bowel Syndrome (IBS) among medical students of King Saud bin Abdulaziz University for Health Sciences (KSAU-HS) and to observe the association between anxiety and IBS. Methods: This cross-sectional observational study conducted during academic year 2015-2016 has used two self-administered, pre-validated questionnaires: Depression Anxiety Stress Scales-21 (DASS-21) and Rome III criteria. The sample size was 270, and proportional allocation was used to determine distribution of this sample across study population based on percentages of students in each academic year. Convenience sampling was used to select participants. Results: The overall prevalence of IBS was 21% (n=57), with a higher prevalence among females (26%, n=23) than males (19%, n=34). IBS was most and least prevalent among first-year students (14%, n=5) and fifth-year students (29%, n=21) respectively. Anxiety levels were normal, mild, moderate, and severe or extremely severe in 39% (n=105), 7% (n=19), 26% (n=70), and 27%. A significant association was found between gender & IBS and anxiety levels & IBS. Conclusion: The prevalence of IBS in this study was 21% and higher among females than males but were highest among fifth-year students for both genders. More than 50% of students had moderate or high levels of anxiety for both genders. The prevalence of IBS was highest among students of 5th fifth year. The study provides evidence that, as medical students of higher year of their under graduation were having higher level of anxiety which leads to IBS.