A 52-year-old male patient presented to the emergency department because of malaise and frequent dizziness. The ECG revealed high-grade atrioventricular block that required placement of a temporary pacemaker. There were no other abnormalities in physical and echocardiographic examination, and coronary angiography excluded the presence of coronary artery disease. IgM and IgG antibodies against Borrelia were positive, and antibiotic therapy with ceftriaxone at the dose of 2 g/die for 15 days resulted in rapid regression of atrioventricular block. Seven-day ECG recording immediately after discharge and 24h ECG monitoring at 40 days confirmed the total disappearance of atrioventricular block. This represents a case of atrioventricular block as the first manifestation of Borrelia infection (Lyme disease). A prompt diagnosis and antibiotic therapy usually result in complete resolution of atrioventricular block without the need for a permanent pacemaker.