Background: Pathologically upstaged T3a renal cell carcinoma (RCC) carries higher oncologic risk than corresponding preoperative clinical stage and presents unique risks from a treatment planning standpoint due to reduced clinician awareness of locally aggressive disease. We sought to identify imaging criteria that predict risk of pathological upstaging of clinical T1 and T2 RCC to T3a and to assess accuracy of CT in detecting T3a RCC. Methods: Single institution retrospective analysis of patients who underwent surgery for RCC. A propensity-score matching process was used to match upstaged patients with non-upstaged (control) patients in a 1:2 fashion. Preoperative CT images were reviewed in a blinded fashion by 2 radiologists for presence of T3a stage imaging criteria. Multivariable analyses assessed risk conferred by imaging features and sensitivity analysis assessed accuracy in detecting T3a RCC. Results: After exclusions, 231 patients were analyzed (mean age 61 years, upstaged 83/control 148, mean tumor size 6.4 cm). In 71/83 (86%) of upstaged tumors, the presence of sinus fat invasion (SFI), perinephric fat invasion (PFI), or venous invasion (VI) was found. The presence of all three was not observed in any non-upstaged tumor. The following features were associated with upstaging: tumor necrosis (OR 2.1, p=0.017), irregular tumor edge (OR 2.9, p<0.001), thickened perirenal fascia (OR 2.6, p=0.001), perinephric stranding (OR 1.8, p=0.043), increased perinephric vascularity (OR 2.02, p=0.021), and perinephric nodules (OR 3.4, p=0.020). The SE/SP for tumor necrosis, irregular tumor edge, thickened perirenal fascia, perinephric stranding, increased perinephric vascularity, and perinephric nodules were 42%/74%, 74%/50%, 48%/74%, 70%/44%, 70%/46%, and 13%/96%, respectively. Conclusions: Upstaged T3a RCC contained several preoperative imaging attributes which were 2-3 times more likely to be present than in non-upstaged tumors. Of these, irregular tumor edge had highest sensitivity, and perinephric nodules had highest specificity. These features should elevate clinical suspicion for T3a disease and may be used to develop a novel risk scoring system. Further investigation is requisite.