Abstract: The authors reported a case of radioactive iodine-refractory differentiated thyroid cancer (RAIR-DTC). The characteristics of RAIR-DTC were analyzed from the aspects of clinical history and ¹⁸F-prostate specific membrane antigen (PSMA) PET/CT imaging. RAIR-DTC has a poor prognosis, and the diagnostic and therapeutic methods are limited. At present, there are few studies on ¹⁸F-PSMA PET/CT imaging in the diagnosis of RAIR-DTC patients. The authors performed ¹⁸F-PSMA PET/CT imaging on a patient with RAIR-DTC, in order to provide new diagnostic and therapeutic methods for patients with RAIR-DTC.