Background: Paroxysmal sympathetic hyperactivity (PSH) is a hyper-adrenergic clinical syndrome that is predominantly described in acquired brain injuries, less commonly in other acquired brain injuries. The association of anti-N-Methyl-D-Aspartate Receptor (NMDAR) encephalitis and PSH is not well established. Case Report: We reported a PSH associated with anti-NMDAR encephalitis and the successful management of this case. A 32-year-old female presented with episodic involuntary movement and rapidly progressed to seizure and acute confusion. Further investigations confirmed the diagnosis of ovarian teratoma associated anti-NMDAR encephalitis which was treated with pulsed methyl-prednisolone, immunotherapy, and ovarian cystectomy. She developed episodic fever, tachycardia, hypertension, diaphoresis, and dystonia during her hospital stay. PSH was suspected after other causes were excluded and the diagnosis was made more probable by applying PSH assessment measure (PSH-AM). A combination of pharmacological agents was started with good response. At 9 months from symptoms onset, she achieved almost complete recovery and returned to work. Conclusion: This case report raises the awareness of PSH in anti-NMDAR encephalitis and illustrates the use of PSH-AM as an assessment tool to diagnose PSH and assess its severity. When PSH was recognized early and treated aggressively, good outcome can be achieved.