Lyme disease is a tick-borne spirochete infection that may affect the heart. Cardiac manifestations include conduction disturbances and other pathologies of the heart. Disturbance of atrioventricular (AV) node conduction is the most common cardiac manifestation of Lyme disease. We report a 61-year old female, who was admitted to the emergency department with the complaints of syncope, dizziness and generalized fatigue. Physical examination revealed normal findings. The patient’s electrocardiogram on admission revealed a newly diagnosed bradycardia due to third degree of AV block with40/min ventricular rate. The patient was admitted to the coronary care unit and was placed a transvenous pacemaker. Lyme serology and Western blot were positive for Borrelia antibodies. The symptoms and AV block resolved completely after doxycycline therapy.