Austempered ductile iron (ADI) has a high potential to substitute alloy steels in power-train applications. However, the machinability of ADI is difficult and tool life is shortened by the appearance of severe adhesive and abrasive wear on tool cutting edge. In this regard, the deposition of a suitable coating could reduce these phenomena. Previous works have investigated the behavior of coated tools on turning or drilling of ADI, but a knowledge gap exists regarding the tapping operation. In this study, the performance of six PVD coatings for the tapping of ADI-900 was investigated. The tools were coated using Cathodic Arc deposition and were analyzed in two sets of experiments. In the first set, four commercial coatings commonly used in cast iron machining were compared: a monolithic AlTiN, a nanostructured AlCrSiN, and two configurations of AlTiSiN (a multilayer and a gradient). Before film deposition, the high speed steel (HSS) substrate surface was micro-blasted. Cutting performance was evaluated by a combined analysis of tool wear, cutting torque data, and SEM-investigations of the tap surface. The best results were yielded by the gradient AlTiSiN (AlTiSiN-G) but coating delamination was also noticeable in the rake face. The application of a drag grinding pre-treatment led to an improvement of the coating adhesion and to a reduction of wear and torque values. In the second set of experiments, AlTiSiN-G was compared to a double layer TiAlCN-DLC coating and to AlTiSiN-18. The results confirmed that the use of HSS taps coated with AlTiSiN-G is a feasible solution for tapping of ADI-900.