A 40-year-old man presented with conductive hearing loss and pressure- and sound-related vestibular symptoms. Computed tomography and diffusion-weighted magnetic resonance imaging revealed the presence of a cholesteatoma involving the vestibular labyrinth. The patient underwent a canal-wall-up tympanoplasty, which revealed evidence of a disruption of the vestibular labyrinth and a wide dehiscence of the vestibule, which was immediately resurfaced. At the 2-month follow-up, the patient's pressure- and sound-related vestibular symptoms had disappeared. Pure-tone audiometry showed a reduction in the air-bone gap with a slight deterioration of bone conduction and an improvement in the air-conduction threshold. Fistulization of the otic capsule produces a “third window,” which can lead to a dehiscence syndrome. One possible cause is a cholesteatoma of the middle ear or petrous bone. When the vestibule is invaded by a cholesteatoma, hearing is almost invariably lost, either pre- or postoperatively. However, in our case, wide opening of the vestibule resulted in hearing preservation.