Here, we report a patient with persistent positional upbeat nystagmus in a straight supine position with no evident abnormal central nervous system findings. A 43-year-old woman with rotatory positional vertigo and nausea visited our clinic 7 days after the onset. Initially, we observed persistent upbeat nystagmus in straight supine position with a latency of 2 s during the supine head roll test. However, an upbeat nystagmus disappeared on turning from straight to the left ear-down supine position, and while turning from the left to right ear-down position, an induced slight torsional nystagmus towards the right for >22 s was observed. In the Dix-Hallpike test, the left head-hanging position provoked torsional nystagmus towards the right for 50 s. In prone seated position, downbeat nystagmus with torsional component towards the left was observed for 45 s. Neurological examination and brain computed tomography revealed no abnormal findings. We speculated that persistent positional upbeat nystagmus in this patient was the result of canalolithiasis of benign paroxysmal positional vertigo of bilateral posterior semicircular canals.