In this study we aim to describe a case of third nerve palsy caused by a chronic ipsilateral subdural hematoma in an awake outpatient and perform a literature review. A 77-year-old man presented with acute painful diplopia and ptosis. Examination revealed complete left third nerve palsy with pupillary involvement. Head computed tomography (CT) and CT-angiography revealed a chronic ipsilateral subdural hematoma with no aneurism, as the cause of the third nerve palsy. He was urgently treated with craniotomy and recovered without sequelae. We reviewed the current literature about third nerve palsy associated to chronic subdural hematoma. Although rare, spontaneous chronic subdural hematoma should be considered in the differential diagnosis of isolated acute painful pupil-involving third nerve palsy in an awake and alert outpatient.