Objectives: We examined the association between the size and cross-sectional area of the superior vestibular nerve as measured on constructive interference in steady-state (CISS) parasagittal magnetic resonance imaging (MRI) and the vestibular nerve function as measured by electronystagmography. Methods: The retrospective observational cohort study took place at an academic tertiary referral center. Twenty-six patients who met established clinical and electronystagmographic criteria for vestibular neuritis and who underwent parasagittal CISS MRI were identified. Two blinded investigators measured vestibular nerve height and width bilaterally at the level of the fundus of the internal auditory canal and calculated the cross-sectional nerve areas. The inter-rater reliability and agreement were analyzed. Symptom duration, age, and gender were also examined. Results: A statistically significant decrease was observed in both vestibular nerve cross-sectional area and height as compared to the contralateral vestibular nerve. A non–statistically significant trend was observed for a relative decreased cross-sectional nerve area with increased age, as well as a decrease in nerve area with an increase in symptom duration. Conclusions: Decreases in both vestibular nerve cross-sectional area and height are observed in patients with unilateral vestibular neuritis as measured on parasagittal CISS MRI.