Background: Criteria for staging of T1 renal tumors into T1a (≤4cm) and T1b (4cm< and ≤7cm) have remained unchanged since 1997. Advancements in tumor biology have noted the heterogeneous potential of T1 renal tumors. We hypothesized that a three-tier classification may more rationally risk stratify T1 renal masses than the current T1a/T1b system. Methods: Multicenter (UCSD, Fox Chase Cancer Center, Ospadele San Raffaele) retrospective analysis of patients with cT1 renal cell carcinoma treated between 1987 and 2018. Patients were stratified into three groups: cT1a (≤2cm, very low risk), cT1b (2cm< and ≤5cm, low risk), and cT1c (5cm< and ≤7cm, intermediate risk). Primary outcome was recurrence free survival (RFS). Secondary outcome was overall survival (OS). Multivariable Cox Regression analysis (MVA) and Kaplan-Meier analyses (KMA) were utilized. Results: 3,324 patients were stratified into proposed T1 groups (T1a=578, T1b=2111, T1c=635; median follow-up 50 months). For cT1a, cT1b and cT1c, KMA revealed 5 year RFS of 96.9%, 91.6%, and 80.6% (p<0.001), and 5 year OS of 91.9%, 86.3%, and 76.2% (p<0.001). MVA for RFS revealed increasing age (HR=1.02, p<0.001), diabetes mellitus (HR=1.36, p=0.04), high tumor grade (HR=2.22, p<0.001) and tumor stage (Referent T1a; cT1b HR=2.18 p=0.001, cT1c HR=5.01 p<0.001) as independent risk factors. MVA for OS revealed increasing age (HR=1.05, p<0.001), diabetes mellitus (HR=1.57, p<0.001), high tumor grade (HR=1.34, p=0.002) and tumor stage (Referent T1a; cT1b HR=1.26 p=0.1, cT1c HR=2.050 p<0.001) as risk factors. Conclusions: Subclassification of cT1 renal cell carcinoma into three clinical stage categories corresponds to distinctive tumor groups whose biological potential varies significantly. Division into three distinct categories may enhance risk stratification, refine preoperative counseling, and augment postoperative follow-up protocols by delineating a very low risk and intermediate risk subset of renal tumors.