Purpose <p>To explore the influence of perirenal collateral (PRC) on the operation and prognosis of nonmetastatic renal cell carcinoma (RCC) and inferior vena cava (IVC) tumor thrombus.</p> Methods <p>A total of 10,260 patients with RCC who underwent surgical resection were retrospectively collected. Two hundred and forty-one patients (median age, 56.0 years [IQR: 48.0, 63.0], 174 males) with pathologically confirmed nonmetastatic RCC and IVC tumor thrombus were analyzed. The presence or absence of abnormal PRC was determined by 3 observers on images. Relevant clinical data, details of the operation, postoperative complications, and pathological results were obtained and compared. The Kaplan-Meier method was used to estimate recurrence-free survival (RFS).</p> Results <p>A total of 185 patients had abnormal PRC on preoperative MR images. Patients with abnormal PRC had significantly larger tumor sizes (<i>P</i> &lt; 0.001), were more likely to have clinical symptoms (<i>P</i> &lt; 0.001), and had positive RBCs in urine (<i>P</i> &lt; 0.001). During the operation, patients with abnormal PRC had a longer operative duration (<i>P</i> &lt; 0.001), more blood loss (<i>P</i> &lt; 0.001), and more red blood cell infusions (<i>P</i> = 0.002). Compared with patients without abnormal PRC, the proportion of open surgery was significantly higher in patients with abnormal PRC (44/185 vs. 5/56, <i>P</i> = 0.001). RFS was significantly shorter (<i>P</i> = 0.002) among patients with abnormal PRC. By multivariate Cox regression analysis, renal sinus fat invasion, perirenal fat invasion, tumor size, and abnormal PRC were independent predictors of RFS (all <i>P</i> &lt; 0.05).</p> Conclusion <p>In patients with nonmetastatic RCC and IVC tumor thrombus, abnormal PRC was associated with intraoperative adverse events and worse RFS. Evaluation of PRC through imaging could help develop treatment plans and provide prognostic information.</p>