In this chapter we try to find an answer to how governance systems for global commons are created and maintained by building a behavioural foundation for collective action. We do this by viewing governance as a public good that must be provided. Like all public goods, global governance is also at risk of being underprovided and subject to free rider behaviour leading to the degradation of a commons. Due to the sheer size and complexity of global commons those problems are aggravated. But solely following that rationale would lead to the acceptance that involved actors are unable to govern global commons collectively. This chapter moves away from that pessimistic view and, by using the classic divide between supply and demand, we identify the challenges and opportunities for global governance to manage commons successfully. Actors are influenced by their past experiences and norms and trust, reputation and reciprocity when we allow for actors to have longer time-horizons leading to the possibility for instating global governance regimes. Instead of understanding governance regimes as separate independent entities, however, in this chapter we view the governance of global commons as being linked to many other governance regimes in a polycentric setting. Through polycentricity the need or demand for governance can be better assessed due to increased possibilities for information sharing while governance, through linkage, can also be better fitted for specific situations on the demand side. The explanation of the workings of polycentricity provides the reader with a convincing explanation on how collective action problems on a global scale can be overcome.