Objective The aim of this study is to evaluate the feasibility, safety, and short-term effectiveness of a high-power (150 W) microwave ablation (MWA) device for tumor ablation in the lung, liver, and kidney. Methods Between December 2021 and June 2022, patients underwent high-power MWA for liver, lung, and kidney tumors. A retrospective observational study was conducted in accordance with the Declaration of Helsinki. The MWA system utilized a 150-W, 2.45-GHz microwave generator (Emprint™ HP Ablation System, Medtronic). The study assessed technical success, safety, and effectiveness, considering pre- and post-treatment diameter and volume, lesion location, biopsy and/or cone beam computed tomography (CBCT) usage, MWA ablation time, MWA power, and dose-area product (DAP). Results From December 2021 to June 2022, 16 patients were enrolled for high-power MWA. Treated lesions included hepatocellular carcinoma (10), liver metastasis from colon cancer (1), liver metastasis from pancreatic cancer (1), squamous cell lung carcinoma (2), renal cell carcinoma (1), and renal oncocytoma (1). Technical success rate was 100%. One grade 1 complication (6.25%) was reported according to CIRSE classification. Overall effectiveness was 92.8%. Pre- and post-treatment mean diameters for liver lesions were 19.9 mm and 37.5 mm, respectively; for kidney lesions, 34 mm and 35 mm; for lung lesions, 29.5 mm and 31.5 mm. Pre- and post-treatment mean volumes for liver lesions were 3.4 ml and 24 ml, respectively; for kidney lesions, 8.2 ml and 20.5 ml; for lung lesions, 10.2 ml and 32.7 ml. The mean ablation time was 48 minutes for liver, 42.5 minutes for lung, and 42.5 minutes for renal ablation. The mean DAP for all procedures was 40.83 Gcm². Conclusion This preliminary study demonstrates the feasibility, safety, and effectiveness of the new 150 W MWA device. Additionally, it shows reduced ablation times for large lesions.