The aim of this study is to investigate the relationship between food intake patterns and irritable bowel syndrome in adults in Ahvaz city. In this case-control study, the protocol of which was approved by the Research Vice-Chancellor of Ahvaz Jundishapur University of Medical Sciences (registration number RDC-9809) and the Ethics Committee of Ahvaz Jundishapur University of Medical Sciences (registration number IR.AJUMS.REC.1398.908) 147-item food frequency questionnaire (FFQ) was used to check food intake. Extraction of the dominant food patterns received was done using the principal component analysis (PCA) method, and finally, the different segments of following each food pattern with the risk of irritable bowel syndrome were analyzed using logistic regression and adjustment of confounding factors. 4 dominant food patterns were extracted, which included traditional, unhealthy Western and Mediterranean food patterns. After adjusting for confounding factors, the results showed that following an unhealthy eating pattern was associated with an increased risk of irritable bowel syndrome. Following the Mediterranean diet pattern was associated with a reduced risk of IBS in the unadjusted model (OR=0.49, P=0.03). Although this relationship was not statistically significant in the adjusted models, there was a trend towards risk reduction (P-trend=0.04). There was no significant relationship between following traditional and western food patterns with the risk of irritable bowel syndrome. There is a relationship between following the prevailing dietary patterns and the risk of irritable bowel syndrome. The results of this study showed that following an unhealthy eating pattern was associated with an increased risk and following a Mediterranean eating pattern was associated with a decreased risk of this disease. Future studies could investigate the specific mechanisms through which diet affects IBS, taking into account the role of lifestyle and psychosocial factors.