This report describes a thoracic duct ligation and cysterna chyli ablation in an 11-year-old castrated male Shih Tzu with chylothorax secondary to brachiocephalic vein thrombosis induced by an intravenous pacemaker lead. An angiogram revealed a filling defect in the left external jugular vein cranial to the subclavian vein, which suggested an obstruction along the tract of the pacemaker lead near the venous entrance of the thoracic duct. A thoracic duct ligation was performed, in addition to a pericardiectomy and pleural port placement. Due to persistent chylous pleural effusion, a cisterna chyli ablation was performed. A lymphangiogram pre and post ablation confirmed complete occlusion of the communicating lymphatic vessels. These procedures yielded temporary abatement of pleural effusion.