Carcinoma showing thymus-like element (CASTLE) is a very rare malignant neoplasm in the lower portion of the thyroid gland or soft tissue of the neck. Recurrent laryngeal nerve (RLN) is the most frequent site of CASTLE. Non-RLN is also a rare anomaly. Both CASTLE and non-RLN are risk factors for vocal cord paralysis. In this report, the authors describe a 73-year-old patients diagnosed with CASTLE and non-RLN. During total thyroidectomy, one RLN was sacrificed inevitably because of tumor invasion, while the other non-RLN was successfully saved, which was expected based on preoperative computed tomography (CT). If the diagnosis is uncertain, CT should be checked to prevent unexpected risks.