Purpose <p>Microwave ablation (MWA) with higher-power settings (&gt; 100&#xa0;W) aims to create larger, more uniform ablation zones, potentially reducing local tumour progression (LTP). This post-market clinical follow-up study evaluated the safety and efficacy of higher-power settings for MWA of liver tumours.</p> Methods <p>Patients with colorectal liver metastases (CRLM) and hepatocellular carcinoma (HCC) treated with MWA (&gt; 100&#xa0;W) using the EMPRINT^TMHP generator (Medtronic, Minneapolis, MN, USA) were included. The primary outcome measure was safety, assessed by CTCAE. Higher-power settings were considered safe if complication rates did not exceed those of a historical cohort treated with conventional settings (EMPRINT™; ≤ 100&#xa0;W). Secondary outcome measures included LTP-free survival (LTPFS), local control (LC), sphericity index (SI) and length of hospital-stay.</p> Results <p>One-hundred-and-twenty-three patients were included. Following 97 procedures for CRLM (82 patients), adverse events (AEs) occurred in 13.4%, with serious AEs (SAEs) in 4.1%. In 44 procedures for HCC (41 patients), AEs occurred in 11.4%, with SAEs in 6.8%. The total SAE rate (5.0%) was lower than the historical cohort (5.8%). For CRLM and HCC, 1-, 2-, and 3-year LTPFS was 94.9%, 93.7%, 93.7%, and 95.1%, 92.5%, 92.5%, respectively. LTP occurred in 4.8% of CRLM (vs. 6.9% in historical cohort; <i>p</i> = 0.38) and in 6.3% of HCC. LC was 100%. Median hospital-stay was 1 day. Median SI was 0.79 for both CRLM and HCC.</p> Discussion <p>This study indicates that higher-power settings (&gt; 100&#xa0;W) during MWA for liver tumours does not compromise safety or sphericity of the ablation zone. This was supported by low LTP rates and 100% local control.</p> Level of Evidence <p>Level 3</p> Graphical Abstract <p></p>