A rare case of branch retinal artery occlusion (BRAO) following a subtotal thyroidectomy for thyroid cancer in a 58-year-old woman is reported herein. Five days after her thyroidectomy, the patient complained of having had a reduction in visual acuity and visual field loss of the superior nasal side in her right eye since the operation. BRAO was diagnosed following the discovery by funduscopy of inferotemporal branch artery occlusion with retinal edema, hemorrhage, and periarterial sheathing in the right eye. Despite immediately puncturing the anterior camera and massaging the eyeball while administering intravenous anticoagulant therapy, the visual field disturbance remained unchanged. The most common causative factor of postoperative sudden BRAO is reported to be emboli. However, in our case, the most likely cause was the stretching and pressure exerted on the carotid artery with consequent atheromatous plaque formation at the time of thyroidectomy.