Stage IV lung cancers are often characterized by widespread systemic metastases, including pleural and cardiac sites. We report the case of a 67-year-old man admitted for suspected advanced lung cancer with bilateral pleural and pericardial effusion. Echocardiography revealed an intracardiac mass with heterogeneous echogenicity (hypo/isoechoic) adherent to the anterior wall of the right ventricle, associated with mild impairment of right ventricular systolic function and a mild-to-moderate pericardial effusion without clinical signs of tamponade. Whole-body positron emission tomography (PET) confirmed hypermetabolic pulmonary nodules and widespread secondary lesions, including myocardial involvement. This case highlights the crucial role of integrated imaging techniques, particularly the combination of echocardiography and PET, in the early detection of cardiac metastases. A multidisciplinary approach, involving oncologists, cardiologists, and radiologists, was fundamental to define an accurate clinical framework and the appropriate therapeutic strategy. Unfortunately, the premature death limited the possibility of targeted therapy. Advanced imaging modalities are confirmed to be essential for the personalized management of complex oncologic patients.