The detection of a heart murmur in paediatric patients may mask silent arrhythmias with potential hemodynamic consequences. The paper reports the case of an otherwise asymptomatic 2.5-year-old boy, presenting with slight growth retardation, bradycardia (50-60 bpm) and a systolic murmur. Diagnostic workup, including ECG and echocardiogram, revealed a complete atrioventricular (AV) block with a junctional escape rhythm and mild left ventricular dilation. After ruling out secondary, autoimmune and infectious causes, a diagnosis of idiopathic complete AV block was made. The patient remains under cardiological surveillance to monitor cardiac function and determine the future necessity of pacemaker implantation