Objective: Imaging plays a critical role in the evaluation of patients presenting with unilateral vocal fold paresis or paralysis of unknown etiology. In those with idiopathic unilateral vocal fold paralysis (iUVFP), there is no consensus regarding the need or timing of repeat imaging. This study seeks to establish the rate of delayed detection of alternate etiologies for these patients to determine if and when imaging should be repeated. Methods: Retrospective chart review was conducted identifying patients at our institution with vocal fold movement impairment between 1998 and 2014. Idiopathic paralysis was diagnosed if physical examination, laryngoscopy, and initial imaging excluded a cause. Demographic data, length of follow-up, and the presence of late lesions were noted. Time to detection was plotted using the Kaplan-Meier method. Results: Of 3210 patients reviewed, 207 had a diagnosis of iUVFP. Of these patients, 8 went on to develop alternate diagnoses, including pulmonary disease, skull-base and laryngeal neoplasms, and thyroid malignancy. In Kaplan-Meir analysis, 90% remained “idiopathic” at 5 years of follow-up. The mean time to detection was 27 months. Conclusions: Patients initially diagnosed with iUVFP may have an occult cause that later becomes evident. We recommend repeat imaging within 2 years after diagnosis, but this is likely unnecessary beyond 5 years.