An 83-year-old man with acute inferior wall myocardial infarction underwent successful percutaneous coronary intervention for right coronary artery. Subsequent echocardiography 3 days later showed an incidental huge cardiac chamber compressing left atrium. The chamber was found to have a narrow neck connecting with left ventricle, suggestive of a pseudoaneurysm. Real-time 3-dimensional echocardiography could clearly demonstrate the spatial relationship between pseudoaneurysm and corresponding cardiac chambers, and its precise location and the orifice of pseudoaneurysm. A myocardial break-out point resembling a bird beak with a flap could also be clearly seen and quantified by real-time 3-dimensional echocardiography. This patient underwent surgical resection and the serial follow-up remained uneventful.