A 61-year-old woman suffered transient mydriasis and prolonged facial nerve palsy after intracisternal papaverine application subsequent to elective clipping of an unruptured middle cerebral artery aneurysm. The mydriasis resolved within 90 minutes, but the facial nerve dysfunction persisted for 2 months before complete recovery. Prolonged irrigation of the cisterns may have washed the papaverine into contact with the facial nerve. This case supports previously reported evidence of a possible effect of topical intracisternal papaverine hydrochloride application on the facial nerve.