The endoscopic approach to adrenal glands has been limited to laparoscopic and retroperitoneal access due to the relative inaccessibility of the retroperitoneal space in the former case and to the limited working space in the latter. We undertook this study to investigate the possibility of performing a left adrenalectomy through a thoracoscopic transdiaphragmatic approach in a swine model. Five pigs were anesthetized, intubated, and ventilated. Four laparoscopic trocars were inserted and a left pneumothorax was accomplished by CO2 insufflation. A peripheral posterior phrenotomy was made starting from the aortic hiatus and extended laterally for about 6 cm. The resulting pneumoretroperitoneum facilitated the subsequent identification of anatomic structures, allowing an easy exposure of the left adrenal gland. The gland was progressively dissected downward, interrupting the tributary vessels with endoscopic clips, and it was finally extracted through one of the trocar ports. Adrenalectomy was accomplished in all the animals without intraoperative mortality. Complications included splenic injury with prolonged bleeding and difficulty in performing the diaphragmatic suture (one case each). Through this approach direct and rapid exposure of the left adrenal gland was allowed, and adrenalectomy was accomplished in all the animals. These results suggest further investigations of the clinical application of this procedure.