A dehiscent high jugular bulb would be a pitfall in middle ear surgery especially for cholesteatoma. We report a case of cholesteatoma attached to a dehiscent high jugular bulb successfully treated with surgery assisted with underwater endoscopy. To the best of our knowledge, no previous study has reported a case of cholesteatoma with dehiscent high jugular bulb treated with surgery assisted with underwater endoscopy. Owing to the risk of jugular bulb injury, underwater endoscopy is a good indication for middle ear cases with a dehiscent high jugular bulb to obtain a clear operative field and avoid an unexpected air embolism.