We report a case of a 33-year-old nulliparous woman who, following a short prodromal illness, experienced a series of psychiatric and behavioural symptoms. These included states of terror, insomnia, delirium, self-harm and suicidal ideation, facial dyskinesias, verbigeration, cognitive impairment, reduced responsiveness, violence and paranoia. A diagnosis of anti-N-methyl-D-aspartate (NMDAR) encephalitis was made 50 days after symptom onset. Early tumour removal is associated with an improved prognosis and a laparoscopic oophorectomy was performed following detection of a dermoid cyst. Within 24 hours of the operation there was marked improvement in cognitive function and appetite.