Otologic surgery and surgical drilling of the skull are well known precipitating factors of secondary benign paroxysmal positional vertigo (BPPV). Especially if BPPV is developed after ear surgery, operated ear has been thought as the side of BPPV with little doubt. Recently we experienced a patient of BPPV developed 3 days after mastoidectomy. Positional test showed nystagmus with pure horizontal component and it was geotropic direction changing nature depending on the head position. Initial location of the particles was assumed in the lateral semicircular canal of operated ear, but following repositioning maneuver, positional nystagmus was compatible with anterior semicircular canal of contralateral ear. With this case report, authors suggest plausible mechanisms of the contralateral side BPPV after mastoid surgery as follows. Surgical position during mastoid surgery (contralateral ear down) and postoperative bulky mastoid compressive dressing usually kept the patient's head to the contralateral side can be precipitating factors for migration of detached particles into the semicircular canal of dependent position. Anyway, appropriate differential diagnosis and management plans should be prompted using bed side vestibular evaluation, since serious irreversible inner ear complications are more frequent cause of postoperative vertigo than BPPV.