BACKGROUND: Most studies assessing the influence of a low fermentable oligo-, di-, monosaccharides and polyols (FODMAP) diet on irritable bowel syndrome (IBS) symptoms were clinical trials with a small sample size. OBJECTIVE: This study was done to examine the association between adherence to a low FODMAP diet and symptoms of irritable bowel syndrome in Iranian adults. METHODS: In this cross-sectional study, data on 3362 Iranian adults were collected. Dietary intakes of study participants were assessed using a validated 106-item self-administered dish-based, semi-quantitative food frequency questionnaire. Based on earlier studies, we identified all foods with a high FODMAP content in our dataset. Participants were categorized into quartiles in terms of dietary intakes of these foods. Total FODMAP score for each individual was computed by summing up the scores of all foods. Individuals in the highest quintile of FODMAP score were defined as those with the greatest adherence to the low FODMAP diet. A modified Persian version of the ROME III questionnaire was used for assessment of IBS, which was defined according to ROME III criteria. RESULTS: Adherence to the low FODMAP diet was significantly associated with low intakes of macro- and micro-nutrients as well as all food groups (P < 0.001 for all). Participants with the greatest adherence to the low FODMAP diet, compared to those with the lowest adherence, had not significantly lower odds for having IBS, either before (95% CI 0.93, 1.58, P < 0.05) or after adjustment for potential confounders (95% CI 0.80, 1.60, P < 0.05). This was also the case for IBS subtypes; such that those with the greatest adherence to the low FODMAP diet, compared to those with the lowest adherence, were not less likely to have these types of IBS. CONCLUSION: In conclusion, we did not find any significant association between adherence to the low FODMAP diet and IBS. Further studies are required to reach a definite conclusion in this regard.