Purpose To evaluate the long-term efficacy of image-guided cryoablation of sporadic clinical T1 (cT1) biopsy-proven renal cell carcinoma (RCC) and the technical success and safety of all cryoablation treatments. Materials and Methods For this retrospective single-institution study, 433 patients (median age, 68 years; range, 19-90 years), of whom 293 were men (median age, 69 years; range, 19-90 years) and 140 were women (median age, 68 years; range, 30-89 years), who had 484 cT1 renal masses (mean size, 33 mm) and who were treated between 2007 and 2016 were identified from a prospectively maintained tumor registry. Treatment efficacy for all treated lesions and complication rates of all procedures were computed. Oncologic outcomes for a subset of 220 patients with sporadic biopsy-proven RCC were analyzed. The Kaplan-Meier method was used to estimate local recurrence-free survival (LRFS), metastasis-free survival (MFS), and overall survival (OS) rates. Results Of the 484 treated cT1 renal masses, 474 were imaged subsequently, with a primary treatment efficacy of 96% (453 of 474), increasing to 98% (465 of 474) after secondary ablation, and a major complication rate (Clavien-Dindo grade ≥ III) of 4.9% (23 of 473 procedures). The estimated LRFS and MFS rates, respectively, for the 220 patients with biopsy-proven RCC were 97.2% (95% confidence interval [CI]: 92.6%, 99.0%) and 97.7% (95% CI: 93.3%, 99.1%) at 3 years and 93.9% (95% CI: 85.8%, 97.4%) and 94.4% (95% CI: 86.7%, 97.7%) at 5 years. The estimated OS of all 433 patients was 91.7% (95% CI: 87.5%, 94.5%) and 78.8% (95% CI: 71.1%, 84.6%) at 3 and 5 years, respectively. Conclusion Five-year oncologic outcomes after image-guided cryoablation for clinical T1 renal cell carcinoma are competitive with those of resection at a lower complication rate. © RSNA, 2018.