Post-operative coronary artery spasm, a rare but potentially fatal complication following cardiac surgery, warrants significant attention. This report discusses a 64-year-old male who suffered a severe coronary artery spasm leading to cardiac arrest following surgery. Initially stable, the patient rapidly developed critical ventricular arrhythmias and hypotension, resulting in cardiac arrest four hours post-surgery. Emergency coronary angiography revealed extensive spasms, successfully managed with intracoronary nitroglycerin. This case stresses prompt recognition and management of coronary artery spasm after non-coronary cardiac procedures, underscoring coronary angiography's vital role in diagnosis and treatment.