A 50-year-old man presented with chest pain symptoms for 7 years. He did not report any other complaints. The diagnostic tests including physical examination, routine laboratory tests, chest x-ray, and electrocardiography were reported as normal. Cardiac MRI, however, revealed a 64 X 66 mm mass lesion in the left myocardium. He was referred to our unit for further tests. A PET/CT was carried out which demonstrated a minimally increased fluorodeoxyglucose uptake at the peripheral margins of the mass, which deemed to be suspicious for malignancy. The patient underwent a thoracotomy and the cardiac mass was excised. Histopathologic examination reported this lesion as a hydatid cyst.