Introduction: IRRITABLE BOWEL SYNDROME (IBS) is the most common functional gastrointestinal disorder, which is characterized by the presence of abdominal pain or discomfort associated with altered BOWEL habits. This systematic review aimed to assess the nutritional factors (dietary patterns and food groups) associated with IBS. Methods: Articles were collected via searching in databases such as Medline, EMBASE, CINAHL, ProQuest, PubMed, Scopus, ScienceDirect, and Google Scholar using relevant keywords and phrases, including IRRITABLE BOWEL SYNDROME, pattern, intake, behavior, habit, meal, nutrition, food, lifestyle, and prevalence. The articles were confined to the original human studies that were published in English since 2010. Duplicates and unrelated materials were excluded. Results: Consumption of processed meat, fast foods, and legumes has been reported to increase the risk of IBS. However, the correlation between the consumption of milk, fruits, and vegetables has not been conclusive. Moreover, the association between cereal intake and risk of IBS varies depending on the type of cereals. The results also indicated that fast food dietary patterns increased the risk of IBS, while lacto-vegetarian dietary patterns reduced the risk of IBS. Conclusion: According to the results, the effects of some food groups on IBS are unclear. In addition, research in this regard is limited to food patterns, and further investigations are required in order to reach conclusive results.