A Thornwaldt's cyst is an uncommon nasopharyngeal lesion that develops from the remnant of the primitive notochord. A 65-year-old man with a Thornwaldt's cyst is presented in this case report. The patient was diagnosed by rigid nasal endoscopy and magnetic resonance imaging (MRI). These cases are infrequently presented in the English journals. Our study suggested that endoscopic and MRI examinations of the nasopharynx were a simple, rapid, and useful procedure for the diagnosis of the Thornwaldt's cysts.