Objectives: Sudden sensorineural hearing loss (SSNHL) may occur in post-irradiated nasopharyngeal carcinoma (NPC) survivors with a rare rate. This study was conducted to evaluate the clinical characteristics and prognosis of this population. Study Design: Retrospective cohort study. Setting: Tertiary otology referral center. Patients: Five hundred ninety nine SSNHL patients were recruited between January 2010 and January 2019. Patients were divided into two groups: NPC group (n = 24) and non-NPC group (n = 575). Interventions: All SSNHL patients were diagnosed by pure tone audiometry and treated with steroids, blood flow promoting agents, and hyperbaric oxygen therapy. Main Outcome Measures: We evaluated the clinical characteristics and prognosis of post-irradiated SSNHL and identified prognostic factors by logistic regression analysis. Results: In the NPC group, the initial hearing threshold, contralateral hearing threshold, rate of vertigo, rate of profound hearing loss were all higher than in the non-NPC group (p < 0.05). Hearing gains and the rate of good recovery (both complete recovery and partial recovery) were lower in the NPC group than in the non-NPC group (p < 0.05). Logistic regression analysis revealed that NPC was significantly associated with poor hearing recovery (OR = 3.499, p = 0.040), and that a higher initial hearing threshold and longer treatment delay time were related to a poor prognosis (p < 0.05). Conclusions: SSNHL occurred in post-irradiated NPC survivors often suffered a severe hearing loss with a high rate of accompanying vertigo. NPC may have an adverse impact on the prognosis of SSNHL, and higher initial hearing threshold and longer treatment delay time were indicators of poor hearing recovery.