In contrast to typical atrial flutter, atypical atrial flutter is a heterogeneous group of right and left atrial macro- or localized reentry tachycardias, whose critical component for maintaining the tachycardia is not the cavotricuspid isthmus. Atypical atrial flutter occurs frequently after previous catheter ablation and after cardiac surgical procedures. The intraprocedural success rate during ablation is high, while the recurrence rate depends on structural changes in the atria as well as the underlying mechanism. This chapter provides an overview of the mechanisms as well as mapping and ablation strategies of the most common forms of right and left atrial atypical atrial flutter.