The rights discourse has become a common and powerful currency in the public sphere. Public interest lawyers, who reason in law and facilitate the movements of legal rights, are the currency exchanger that converts power and political momentum, symbolic and formal, between different public entities. This paper adopts a relational framework to understand the presence of public interest lawyers in Taiwan and the complexity of their involvement in promoting, defending, or mobilizing for public good. I systematically analyze the bidirectional relationships that lawyers develop with government (both the administration and the parliament), political party, civil society (including NGOs and the general public), and the court. By examining two types of operation, lawyers in organizations and lawyers in mobilizations, I use the development offour NGOs and four social movements in Taiwan—gender, environment, labor, and China watch—to argue that the expertise of exchange leads to the prevalent role that public interest lawyers are able to play in the twenty-first century.