This chapter discusses the most prominent greenhouse gas (GHG) emissions trading system (ETS) in Asia besides China: South Korea. It examines the interaction amongst South Korean and external actors and ETS models. Policy documents, academic studies and news reports from sources such as Carbon Pulse provided additional insights for our qualitative investigation of external and domestic drivers of eight design elements of the South Korean ETS. The design elements are: Type of system, Ambition level, Allocation mechanism, Coverage, Offsetting, MRV (monitoring, reporting and verification), Price and quantity management, and Revenue earmarking. The interplay between international and domestic dynamics can explain South Korea's decision to use GHG ETS to curb emissions. Interaction with the international carbon market familiarized South Korea with emissions trading. Beginning with a pilot phase and improving the ETS step-by-step resembles the European Union approach, which would indicate a certain degree of inspiration.