Paroxysmal sympathetic hyperactivity (PSH) is characterized by increased activity of the sympathetic nervous system. Although several treatments have been proposed for PSH, their efficacies are uncertain. We report a case of a patient with intractable PSH after pontine hemorrhage who was treated with intrathecal baclofen (ITB). A 61-year-old man was diagnosed with pontine hemorrhage expanding to the bilateral midbrain. Beginning 2 weeks after onset, he developed paroxysmal hyperthermia, tachycardia, tachypnea, hypertension, and generalized dystonic movements. Several medications were administered to the patient, including fentanyl patch, dantrolene, gabapentin, and β blockers. Nevertheless, PSH episodes continued to occur more than twice per day. Seven months after onset, we performed a trial of ITB injection, which led to reduced severity and frequency of PSH. Therefore, the ITB therapy was implanted. Continuous ITB was initiated at a rate of 100 μg/d, which was gradually increased up to 200 μg/d. Oral medications were tapered off. No PSH episode occurred for 4 weeks. Our findings suggest that ITB therapy may be used to manage intractable PSH. Intrathecal baclofen may inhibit postsynaptic activity and suppress sympathetic activity via the stimulation of γ-aminobutyric acid B receptors the brain.