Testicular tumors are almost all malignant tumors and can develop in younger age groups. Testicular tumors are mostly curable, with reported cases of tumor thrombosis within the inferior vena cava being rare. Two patients, aged 35 years and 37 years old complaining of testicular pain and lower abdominal pain were diagnosed with testicular tumors by ultrasound. In addition, tumor thrombus of the inferior vena cava was diagnosed concomitantly at the time of the diagnosis by computed tomography and magnetic resonance imaging. Here, we report testicular tumors accompanied by tumor thrombus, which is an extremely rare finding, with limited reports available. Pathologic diagnoses were seminoma and mixed germ cell tumors, respectively.