We report a 76-year-old man with paradoxical cerebral air embolism. He developed consciousness disturbance and left hemiparesis after a postural change in rehabilitation. CT showed multiple air densities within the right hemisphere. An echocardiography showed a large right-to-left (RL) shunt. We considered the reason to be that a small amount of air entered, and the Valsalva-like maneuver with the postural change moved air into arterial circulation through the RL shunt and embolized a brain artery. The present case showed that even a small amount of air in the venous circulation may become a potential risk for cerebral air embolism, especially in the presence of a large RL shunt.