Objective: To evaluate the diagnostic performance of MRI for the assessment of inferior vena cava (IVC) wall invasion by IVC thrombus in patients with renal cell carcinoma (RCC).Methods: We retrospectively collected patients who underwent radical nephrectomy and thrombectomy for RCC between 2010 and 2018 at Peking University First Hospital. All the patients underwent imaging on a 1.5 Tesla or 3.0 Tesla MRI scanner. Fifty-six patients met the inclusion criteria. Preoperative imaging was reviewed by two radiologists blinded to details of the patient’s surgical procedure and histopathology. Two radiologists measured the maximum anterior-posterior diameter and coronal diameters of the IVC and renal vein, and the craniocaudal extent of tumor thrombus, and evaluated the MRI features of IVC thrombus, including occlusion of the IVC lumen,the margin of the tumor thrombus (smooth vs. irregular), contact of the IVC thrombus and IVC wall, and altered signal of the IVC wall. Univariable and multivariable associations of clinical and radiographic features with IVC wall invasion were evaluated by Logistic regression.Results: Of the 56 patients [male: 43, female: 13, mean age: (55.64±0.43) years], 17 (30.36%) were detected with IVC wall invasion, and most were clear cell carcinoma. Tumor thrombus with IVC wall invasion showed an increase in length of IVC thrombus [(7.91±3.59) cm vs. (5.94±3.57) cm, P=0.049], and more features of complete occlusion of the IVC lumen (P=0.002),irregular margin of the IVC thrombs (P=0.005), contact of the IVC thrombus and IVC wall (P=0.001), and altered signal of the low-intensity vessel wall (P<0.001), with a sensitivity of 94.12% and a specificity of 79.49%.Conclusion: The present study indicates that MRI could be a means of evaluating RCC with IVC wall invasion, and the combination of tumor thrombus length and subjective impression of IVC wall invasion achieved a high sensitivity and specificity for diagnosis.