A 51-year-old man with a 10-day history of acute-onset dysphagia presented with inability to swallow anything orally. The patient was unable to swallow any radiopaque contrast medium; therefore, a videofluoroscopic swallow study could not be performed. Brain imaging, neurological findings, and initial endoscopy findings were normal. Neck computed tomography suggested left vocal cord paralysis. The patient was diagnosed with diabetes one year prior to presentation but did not receive any treatment. Insulin therapy during hospitalization controlled the patient’s blood glucose levels, and his symptoms improved without any sequelae. We present a rare case of vocal cord paralysis secondary to controlled diabetes. The initial endoscopic examination did not include thorough evaluation of the vocal cords; therefore, accurate diagnosis was challenging in this case.