We report a case that illustrates the difficulty in diagnosing left ventricular (LV) pseudoaneurysm and the potential value of cine magnetic resonance imaging (MRI). A 69-year-old man with a history of ischemic congestive heart failure had a mass found on routine chest X-ray, contiguous with the cardiac silhouette. Neither CT nor echocardiography accurately defined the mass. The diagnosis of LV pseudoaneurysm was definitely made by cine MRI. Although the accuracy of various imaging modalities for detecting LV pseudoaneurysm is not known, cine MRI was the most useful test in this case. Despite refusing surgery to correct the pseudoaneurysm, the patient survived for nearly 4 years, treated only with anticoagulation.