Background and Aims: Various modalities have been used to diagnose Meckel's diverticulum (MD) in practice, but with their diagnostic accuracy deemed to be unsatisfactory for clinical practice. Moreover, the usefulness of these modalities has not been evaluated for the diagnosis of bleeding MD in adults, due to the relative rarity of this condition. Therefore, the aim of our multicenter study was to determine the most accurate modality for the preoperative diagnosis of bleeding MD in adults. Methods: We conducted a retrospective analysis of the diagnostic accuracy for small bowel bleeding associated with MD of different modalities in patients >18 years old who underwent assessment for MD, with confirmation at the time of explorative surgery. Diagnostic accuracy of the different modalities was evaluated against the diagnosis obtained using technetium-99m pertechnetatescintigraphy (also known as Meckel's scan), considered to be the gold standard for the diagnosis of bleeding MD in pediatrics. Results: Thirty-five adults were identified with bleeding in MD over the study period, between 2005 and 2012. Among these patients, only 24 (68.6%) were diagnosed with MD preoperatively. The mean (95% confidence interval) diagnostic accuracy of selected modalities was as follows: Meckel's scan, 21.4% (5.7%-51.2%); capsule endoscopy, 35.7% (14.0%-64.4%); balloon-assisted enteroscopy (BAE), 85.0% (61.1%-96.0%); angiography, 0.0% (0.0%-80.2%); computed tomography, 31.8% (14.7%-54.9%); and small-bowel follow-through, 62.5% (25.9%-90.0%). The diagnostic accuracy was significantly higher for BAE than for Meckel's scan (P = 0.001). Conclusions: Among available diagnostic modalities, BAE provides the highest accuracy for the diagnosis of bleeding MD in adults and, therefore, should be considered as the preferred modality for preoperative diagnosis.