The involvement of national courts is essential to the overall effectiveness of arbitration, both inrndomestic and international level. However, anti-suit injunction as an instrument of terminatingrnor staying arbitral proceeding, the relationship of national courts and arbitral tribunals are varyrnbetween forced cohabitation and true partnership. Moreover, a marked increase of anti-suitrninjunctions issued by both Arbitral Tribunals and National Courts has been seen recently. Thisrnthesis, therefore, identifies the power of both national courts and arbitral tribunals towardsrnissuing anti-suit injunction in international arbitration. In addition, compatibility of anti-suitrninjunction with the general purposes and principles of international arbitration have beenrncritically scrutinized. Furthermore, the legal effect of anti-suit injunction in internationalrnarbitration is addressed in detail. Finally, after a profound analysis on the above three areas ofrncontroversies in international commercial arbitration, the thesis argues that since anti-suitrninjunction is a new trend in international arbitration, both National Courts and ArbitralrnTribunals should always exercise this power with due care because their effects may be morernharmful than the problem they are seeking to resolve it.