This paper reports on a case of an omental diaphragmatic hernia revealed during routine anatomical dissection of an obese 85-year-old male with plethoric appearance of the upper body. The hernial mass, with a size of 12 cm x 9 cm, was detected in the anterior mediastinum. It had a long peduncle originating from the transverse colon and passing through the right sternocostal diaphragmatic opening of Morgagni-Larrey. The whole greater omentum was tightly packed and tumid within the serous hernial sac, but without signs of torquation. To our knowledge, this is the first systematic analysis of the omental hernial anatomy by a step-by-step iconography.