This is the first report of conduction system disturbances and slow ventricular tachycardia (VT), related to acute myocarditis associated with cardiac amyloidosis. A 57-year-old female was presented with chest pain and pre-syncope after flu-like symptoms, and was promptly diagnosed with acute myocarditis. The initial electrocardiogram (ECG) revealed complete atrioventricular (AV) block, and transient slow VT was observed after an atropine injection (0.5 mg). This AV conduction disturbance persisted for 12 days, and spontaneously resolved. Left ventricular function was relatively well preserved, and an endomyocardial biopsy revealed acute myocardial inflammation and underlying amyloid deposits. A His-bundle recording, taken 6 weeks after the initial manifestation, indicated normal AV nodal conduction. Endomyocardial biopsies have proven helpful with regard to the diagnosis of acute myocarditis superimposed on amyloidosis, in patients who present with conduction disorder and relatively preserved ventricular function, as was seen in this case.