One of the complications of direct arterial pressure monitoring is drug injection through an arterial line mistaken for an intravenous line. We experienced a case of accidental intra-arterial vecuronium injection through an arterial line on the right radial artery. The incident was noticed just after the injection and the patient was treated by intra-arterial injection of heparin, papaverine, lidocaine and stellate ganglion block. No color change or edema of the right hand was observed until the end of operation. The patient was closely observed after operation and discharged without complication. We report a case of accidental intra-arterial vecuronium injection which was managed successfully.