Haloperidol has been used extensively for the treatment of many psychiatric illnesses as well as for control of agitated patients. Side effects including anticholinergic, extrapyramidal, sedative side effects as well as neuroleptic malignant syndrome are not unusual. Many factors may contribute to these complications including withdrawal or toxicity, concomitant use of other medications or the underlying illness itself. We report a case without previous history of thyroid disorder sufferring acute manic episode. Haloperidol was prescribed to control psychotic symptoms. Symptoms and signs of extrapyramidal syndrome, catatonia and hyperthyroidism ensued. Prescription of anti-thyroid agents and discontinuation of haloperidol were essential in the successful treatment of this patient. It is hypothesized that underlying hyperthyroidism might have precipitated haloperidol neurotoxicity. Haloperidol might play a role in the exacerbation of hyperthyroidism.