Purpose <p>To explore the relationship between vestibular endolymphatic hydrops (EH) and prognosis in acute low-tone sensorineural hearing loss (ALHL) and to analyze the mediating role of cervical vestibular-evoked myogenic potentials (cVEMP).</p> Methods <p>A total of 53 ALHL patients were retrospectively enrolled and divided into good (<i>n</i> = 38) and poor (<i>n</i> = 15) prognosis groups based on clinical outcomes. Vestibular function (cVEMP), imaging findings (vestibular EH via MRI), and electrophysiological indicators were compared. Multivariate logistic regression identified prognostic factors, and ROC curves assessed predictive performance. A mediation model was established using regression analysis and the Bootstrap method.</p> Results <p>No significant differences were observed in baseline characteristics between the two groups (all <i>P</i>&gt;0.05). The incidence of abnormal cVEMP was significantly higher in the poor prognosis group than in the good prognosis group (73.3% vs 31.6%, <i>P</i>=0.006), and the severity of vestibular EH was also markedly greater (<i>P</i>=0.004). Multivariate analysis demonstrated that the severity of vestibular EH (<i>OR</i>=0.251,<i>P</i>=0.009), cVEMP amplitude (<i>OR</i>=0.995,<i>P</i>=0.034), and abnormal cVEMP (<i>OR</i>=0.056, <i>P</i>=0.005) were independent risk factors for poor prognosis. ROC analysis revealed that vestibular EH had high predictive value (AUC=0.768). Mediation effect analysis showed that abnormal cVEMP exerted a mediating effect between vestibular EH and prognosis (indirect effect ab=-0.133, 95%<i>CI</i>: -0.318~-0.025, <i>P</i>=0.044), with a mediating proportion of 38.6%.</p> Conclusion <p>Vestibular EH is closely associated with ALHL prognosis, and this effect may be partially associated with cVEMP dysfunction. As a potential indicator linking structural abnormalities to functional outcomes, cVEMP holds potential clinical value for prognostic assessment in ALHL.</p>