We report the radiologic findings of a rectal carcinoma case with tumor thrombus in the inferior vena cava and left common iliac vein of a 48-year-old woman. The patient complained of swelling in the left leg and consequently underwent a lymphoscintigraphy, CT venography, abdominal CT, PET-CT, pelvis MRI, and ultrasound doppler. The rectal cancer was determined via a colonoscopy. The tissue biopsy of tumor thrombus in the IVC was done during insertion of IVC filter and poorly differentiated adenocarcinoma was revealed by pathology.