Purpose <p>To compare computed tomography guided microwave ablation (MW) and Robot-assisted laparoscopic partial nephrectomy (RAPN) for the treatment of T1a renal cell carcinoma (RCC).</p> Method <p>Retrospective study including patients treated for clinical T1a RCC with either MW or RAPN.</p> Results <p>In total, 71 patients were planned to MW, and 372 patients to RAPN. Patients undergoing MW were older, more comorbid, and had worse kidney function. The median follow-up was 2.4 years (95% CI 2.0, 3.4) and 3.7 years (95% CI 3.1, 4.0) for MW and RAPN, respectively. 6% of patients who underwent MW experienced a major (Clavien Dindo ≥ III) complication compared to 5% following RAPN. In uni- and multivariable logistic regression analyses, there was no significant difference in the risk of experiencing any or a major postoperative complication. The 5-year cumulative incidence of any recurrence was 10% for MW versus 4% for RAPN. The 5-year incidence of a distant recurrence was 0% for MW and 2% for RAPN, respectively. In univariable Cox regression analyses, patients treated with MW had a higher risk of experiencing any recurrence and a local recurrence compared to those who underwent RAPN, HR 4.24 (95% CI 1.26–14.4) for any recurrence and HR 6.95 (95% CI 1.83–26.4) for a local recurrence, respectively. There was no difference in the risk of a distant recurrence between treatment strategies.</p> Conclusion <p>These results indicate that MW has an acceptable safety profile and oncological results, and as such is a feasible treatment option for patients with T1a RCC who are poor surgical candidates.</p>