Purpose To evaluate the various factors that affect renal function following percutaneous radiofrequency ablation (RFA) therapy in patients with renal tumors. Materials and Methods Between 2010 and 2018, 91 patients diagnosed with renal tumors using ultrasonography and CT-guided RFA were enrolled. We retrospectively investigated the serum creatinine (SCr) level and estimated glomerular filtration rates immediately prior to RFA and during post-treatment follow-up. The patients were divided into two groups based on the degree of change in SCr level (0.3 mg/dL). Group comparisons were performed using univariable and multivariable logistic regression analyses to determine the factors impacting renal function. Results Impaired renal function was associated with solitary kidney, chronic kidney disease (CKD) over stage 3, and pyeloureteral injury. Sex, age, other cancers, tumor size, location, growth pattern, and proximity to the collecting system were not significantly associated with impaired renal function. There was a difference in the overall change over time between the association with and without solitary kidney, CKD stage 3, and pyeloureteral injury. Conclusion Among the medical conditions present prior to RFA, solitary kidney and CKD over stage 3 could be considered as risk factors for impaired renal function. Post-procedural pyeloureteral injury can also be considered a risk factor.