This article examines dilemmas of the multistakeholder mechanism of participation in Mexico—situated in the context of the post‐2015 Agenda for Sustainable Development—to rethink the interplay between contemporary diplomacy, global politics, and nongovernmental actors. The central argument is that diplomacy has to open up and function as a collaborative space that includes nongovernmental actors who, in turn, influence the design of contemporary institutions. This, I contend, ultimately leads to a redefinition of relations between governments and societies under a more democratic, inclusive design and code of conduct. The case of the nongovernmental organization campaign “Beyond2015” in Mexico is used in the above context. I evidence, through a qualitative analysis, that the particular multistakeholder mechanism encouraged both at the United Nations level and the Mexican Secretariat of Foreign Affairs, held important limitations for developing an effective inclusive mechanism for certain nongovernmental actors.