Objective: We report a case of Charles Bonnet syndrome (CBS) with visual hallucinations caused by a meningioma that was successfully treated using Yi-gan san (YGS) without surgery. Case Report: An 83-year-old male patient with a known giant olfactory groove meningioma developed visual hallucinations and irritability. CBS was suspected, thus YGS was prescribed at 7.5 g/day. After 2 weeks, his symptoms had resolved. Conclusions: Our findings suggest that treatment with YGS may help ameliorate visual hallucinations and improve the quality of life of elderly dementia patients.