Atrioventricular (AV) block following radiofrequency (RF) ablation for the treatment of AV nodal re-entrant tachycardia (AVNRT) is a rare but serious complication of this procedure. Almost all such cases occur during or immediately after radiofrequencey (RF) energy application, followed by prompt recovery. The present report describes a 22-year-old woman with first-degree AV block on electrocardiography, who developed complete AV block 1 week after RF ablation for the treatment of the uncommon form of AVNRT (slow/slow). The patient's complete AV block persisted for another 1 week before she recovered.