An original technique for performing endoscopic thyroidectomy using a breast approach to avoid an operative scar in the neck was developed. The subcutaneous space in the breast area and the subplatysmal space in the neck were bluntly dissected through a 15-mm incision between the nipples, and CO2 was insufflated at 6 mm Hg to create the operative space. Three trocars were inserted at the breast, and dissection of the thyroid and division of the thyroid vessels and parenchyma were performed endoscopically using an ultrasonically activated scalpel. Four hemithyroidectomies and one partial resection of the thyroid for five female patients with thyroid adenomas 5 to 7 cm in diameter were successfully performed using this procedure. There were no conversions to open surgery or complications. No scars were apparent in the neck, and all patients were fully satisfied with the cosmetic results. Endoscopic thyroidectomy using a breast approach and low-pressure subcutaneous CO2 insufflation is a feasible and safe procedure, which results in satisfactory cosmetic results.