Objective To evaluate the feasibility, efficiency, and safety of microwave ablation (MWA) for T1N0M0 papillary thyroid carcinoma (PTC) with capsular invasion (CI). Methods The data of 69 T1N0M0 PTC with CI underwent MWA from August 2015 to January 2020 were retrospectively analyzed. All PTC nodules were pathologically confirmed by fine needle aspiration (FNA). The extended ablation was performed in all cases, that is, the ablation zone completely covered the tumor and extended the tumor edge by at least 2 mm. The strategy of fluid isolation was successfully applied before and during ablation. The strategy of multiple point ablation was applied. After ablation, the changes in tumor size at different time points, local recurrence, new lesions, lymph node metastasis (LNM), and complications were evaluated and recorded. The technical feasibility, technical success rate, and safety were analyzed. Results Based on the contrast-enhanced ultrasound results, complete ablation has been achieved in all enrolled cases after ablation. The mean maximum tumor diameter and the mean volume of PTC nodules before ablation were 0.84 +/- 0.39 cm (range, 0.3-2 cm) and 0.26 +/- 0.35 ml (range, 0.01-1.72 ml) respectively. The mean follow-up time was 26 +/- 10 months (range, 9-48 months). Nodules in 47 cases (68.1%) completely disappeared in the follow-up period. No local recurrence was detected. The incidence of new lesions and LNM was 4.3% (3/69) and 4.3% (3/69) respectively. Further ablations have been successfully employed for all of the new lesions and LMN. Light voice changes (2.9%, 2/69) were the only major complication, which was relieved within 6 months after MWA. The sizes of the ablation zone increased firstly within 6 months after MWA compared with the pretreatment tumor size (p < 0.05). Twelve months later, the sizes were smaller than those before MWA (p < 0.05 for all). Conclusions MWA is an effective, safe, and feasible method in treating T1N0M0 PTC with CI.