Sonography and transthoracic echocardiography (TTE) are seldom used for assessment of metastatic tumor thrombi in the cardiovascular system in routine clinical practice. We performed this retrospective study to evaluate the combination of sonography with TTE for diagnosis of metastatic tumor thrombi in heart and systemic vessels. Vascular, abdominal, pelvic, and small-part sonography was applied in 18 patients, and TTE was conducted simultaneously in 14 patients. Tumor thrombi invaded into the inferior vena cava system in 12 patients, superior vena cava system in 5 patients, and aorta in 1 patient; they extended to the right cardiac chambers in 11 patients. Six patients had diagnoses by pathologic examination. The primary neoplasms were identified by conventional imaging in 17 patients. The morphologic and echogenic characteristics of the tumor thrombi were diverse and depended on their original tumors. The thrombi were either contiguous or discrete from the original tumors. The neoplastic vascularity of the thrombi and the invasive extension were the primary characteristics that distinguished them from bland thrombi. Simultaneous application of sonography and TTE is a feasible way to comprehensively evaluate cardiovascular metastatic tumor thrombi in most patients.