Although the gold standard in the management of kidney tumors is surgical treatment, thermal ablation methods are a viable therapeutic option for patients with small (<4 cm) renal masses who are poor surgical candidates. The aim of this study was to compare the technical success, primary efficacy and complication rate of percutaneous radiofrequency and microwave ablation in the treatment of small renal masses. A retrospective analysis of consecutive patients with small renal masses treated with radiofrequency or microwave ablation between December 2017 and January 2022 was conducted. Response to the ablative therapy was assessed on contrast-enhanced computed tomography examination after 3 months. Ablations of 44 kidney lesions were performed in 43 patients. Sixteen lesions were treated with radiofrequency and 28 with microwave ablation. Both methods were associated with high technical success (100%). Primary efficacy rates of radiofrequency and microwave ablation were 81.3% and 89.3%, respectively. Ablation-related complications were noted only in the patients treated with microwave ablation (18.5%), all of them being low grade (Clavien-Dindo 1 and 2). Radiofrequency and microwave ablation exhibited comparable efficacy in the treatment of small renal masses. Microwave ablation was associated with a comparatively higher number of complications.