The ongoing WTO plurilateral negotiations could break the stagnation of WTO multilateral negotiations and bring TSDCs into WTO law. However, these negotiations still leave much to be desired. This chapter argues that WTO members should establish a sustainable development club within the WTO to constitutionalise the organisation, thereby incorporating the TSDCs required for the sustainability test into WTO rules. Why is the sustainable development club necessary for constitutionalising the WTO? Would WTO members accept this approach? This chapter addresses these two questions. The chapter begins by introducing the concept of the sustainable development club and explaining its implications for the constitutionalisation of the WTO. It also recognises that the sustainable development club, as a plurilateral mechanism, could undermine the WTO’s multilateral negotiation system. This chapter explains why WTO members must adopt this plurilateral strategy to facilitate negotiations on TSDCs. Additionally, it discusses how to minimise the side effects of this approach and anticipates the difficulties and opportunities that the sustainable development club will encounter.