The advent and development of soft law in international arbitration is no new phenomenon. More than thirty years ago, a proposition was advanced that soft law has become nearly indispensable in international arbitral practice (Reisma nn, 1988). Today, while there are many who fully support this proposition, a growing number of actors in international arbitration generally take a critical stance regarding the non-consensual use of soft law in arbitral proceedings. The aim of this chapter is to analyse these two poles in order to examine the current state of soft law in international arbitration. This chapter first discusses the theoretical concepts of soft law in international arbitration. Then, the application of soft law in international arbitration is explored, by taking into account its relevance to commercial and investment arbitration. Finally, prominent soft law instruments pertaining to procedure, ethics and the merits of an arbitration case will be assessed briefly both in terms of reasons for their development and reception in practice. The chapter concludes with some reflections on the role of soft law in today’s arbitral practice and possible future developments.