Postoperative vertigo after tympanomastoidectomy can be attributed to several causes such as inner ear damage due to excessive ossicle handling, labyrinthitis, BPPV resulting from vibration of drilling, iatrogenic lateral semicircular canal damage, and perilymphtic fistula. Differential diagnosis is critical for the proper management and prognosis of accompanied sensorineural hearing loss, but it may be difficult in some cases. Especially it is quite difficult to distinguish between the serous and suppurative labyrinthitis. In this article we present a case with simultaneous serous labyrinthitis and BPPV. The patient developed whirling vertigo and hearing loss on the 5th day after tympanomastoidectomy. After conservative treatment with steroid and antibiotics, his hearing recovered to preoperative level. We retrospectively reviewed the pitfalls to make a correct diagnosis in this patient and the serial change in nystagmus during the treatment period. The usefullness of the rotation chair test to predict the prognosis of sensorineural hearing loss in labyrinthitis was also discussed.