A mass lesion occupying the left ventricle was noted on a screening CT scan in a 42-year-old man with a history of malignant melanoma. Subsequent echocardiography and cardiac MR imaging provided further hemodynamic and anatomic characterization of the lesion. These studies were also essential in guiding the proper surgical approach to allow extensive resection of the large mass without disrupting cardiac structures and function. The unique clinical aspects of this case are the unusual location for a lone cardiac metastasis of melanoma and the asymptomatic presentation despite the large size of the tumor and its apparent obstruction of ventricular outflow. The clinical and imaging features of this patient's threatening cardiac lesion are presented.