Objectives. To evaluate therapeutic potential of the immunoglobulin G (IgG)-based elimination diet among migraine patients with irritable bowel syndrome (IBS). Background. Food elimination has been suggested as an effective and inexpensive therapeutic strategy in patients with migraine and concomitant IBS in the past studies. Methods. A total of 21 patients (mean [standard deviation] age: 38.0 [11.2] years; 85.7% females) diagnosed with migraine and IBS were included in this double-blind, randomized, controlled, cross-over clinical trial composed of baseline (usual diet), first diet (elimination or provocation diets), and second diet (interchange of elimination or provocations diets) phases and 4 visits. Results. IgG antibody tests against 270 food allergens revealed mean (standard deviation) reaction count to be 23.1 (14.1). Compared with baseline levels, elimination diet per se was associated with significant reductions in attack count (4.8 [2.1] vs 2.7 [2.0]; P<.001), maximum attack duration (2.6 [0.6] vs 1.4 [1.1] days; P<.001), mean attack duration (1.8 [0.5] vs 1.1 [0.8] days; P<.01), maximum attack severity (visual analog scale 8.5 [1.4] vs visual analog scale 6.6 [3.3]; P<.001), and number of attacks with acute medication (4.0 [1.5] vs 1.9 [1.8]; P<.001). There was a significant reduction in pain-bloating severity (1.8 [1.3] vs 3.2 [0.8]; P<.05), pain-bloating within the last 10 days (3.2 [2.8] vs 5.5 [3.1]; P<.05), and improvement obtained in quality of life (3.6 [1.4] vs 2.9 [1.0]; P<.05) by the elimination diet as compared with provocation diet. Conclusions. Our findings indicate that food elimination based on IgG antibodies in migraine patients who suffer from concomitant IBS may effectively reduce symptoms from both disorders with possible positive impact on the quality of life of the patients as well as potential savings to the health-care system.