Systemic lupus erythematosus (SLE), a connective tissue disease characterized by the production of auto-antibodies and immune complexes, can affect all organs including the heart. The involvement of the conduction system in SLE has been less commonly described. We report a case of an asymptomatic 45-year-old woman with SLE referred to the emergency department (ED) for thrombocytopenia, and was found to have alternating first- and second-degree atrioventricular block (AVB) during routine electrocardiographic screening for hospital admission. Serial electrocardiograms (ECG) done in the ED when compared to those recorded 24 h prior revealed progression from mild first-degree AVB (PR interval = 216 ms) to significant first-degree AVB (PR interval = 510 ms), followed by second-degree AVB (Mobitz type I-Wenckebach phenomenon). The conduction abnormalities recorded over a 28-h period resolved with corticosteroid treatment. Review of the literature on the disruption of the cardiac conduction system in SLE is discussed.