Summary Background A low fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP) diet is effective in treating irritable bowel syndrome (IBS). Aim To compare the effects of gut‐directed hypnotherapy to the low FODMAP diet on gastrointestinal symptoms and psychological indices, and assess additive effects. Methods Irritable bowel syndrome patients were randomised (computer‐generated list), to receive hypnotherapy, diet or a combination. Primary end‐point: change in overall gastrointestinal symptoms across the three groups from baseline to week 6. Secondary end‐points: changes in psychological indices, and the durability of effects over 6 months. Results Of 74 participants, 25 received hypnotherapy, 24 diet and 25 combination. There were no demographic differences at baseline across groups. Improvements in overall symptoms were observed from baseline to week 6 for hypnotherapy mean difference (95% CI): −33 (−41 to −25), diet −30 (−42 to −19) and combination −36 (−45 to −27) with no difference across groups (P = 0.67). This represented ≥20 mm improvement on visual analogue scale in 72%, 71% and 72%, respectively. This improvement relative to baseline symptoms was maintained 6 months post‐treatment in 74%, 82% and 54%. Individual gastrointestinal symptoms similarly improved. Hypnotherapy resulted in superior improvements on psychological indices with mean change from baseline to 6 months in State Trait Personality Inventory trait anxiety of −4(95% CI −6 to −2) P < 0.0001; −1(−3 to 0.3) P = ns; and 0.3(−2 to 2) P = ns, and in trait depression of −3(−5 to −0.7) P = 0.011; −0.8(−2 to 0.2) P = ns; and 0.6(−2 to 3) P = ns, respectively. Groups improved similarly for QOL (all p ≤ 0.001). Conclusions Durable effects of gut‐directed hypnotherapy are similar to those of the low FODMAP diet for relief of gastrointestinal symptoms. Hypnotherapy has superior efficacy to the diet on psychological indices. No additive effects were observed.