A B S T R A C TOut-of-hospital cardiac arrest (OHCA) remains a challenge for physicians since effective management and definitive salvage depend upon correct determination of the etiology and the extent of injury. Definitive diagnosis of organophosphate poisoning (OP) requires physicians' clinical awareness of a typical toxidrome, that is, characteristic signs and symptoms of poisoning, and laboratory confirmation.Here we report a case of an OHCA patient with OP, which was initially misdiagnosed as an acute ST segment elevation myocardial infarction based on the patient's medical history and clinical manifestations.