This paper aims to analyze how changing patterns about notions of “actor” and “order” in international relations inform the practices of diplomacy through the framework of complexity theory in an age of uncertainty. To this end, concepts in complexity theory—nonlinearity, network, emergence and co-evolution—are used as analysis tools to revisit actor and order. The main findings of the research suggest that changing global dynamics lead to the emergence of a complex adaptive international system encouraging scholars and practitioners to rethink actor and order. Four findings about the practice of diplomacy also emerge due to this new theoretical analysis: First, understandings of order in the international system have evolved to reflect a more regional-centered approach rather than a global one. Second, the diversification of actors and interactions in the international system directly change the nature of diplomacy, now conceived as a process that evolves in a networked-based relationship. Third, the dominant consequences of participating in a complex, adaptive system are interdependence and co-evolution between actors within diplomacy. Lastly, policymakers have increased their ability to navigate inherent uncertainties and expand the purview of diplomacy to include non-traditional diplomatic agents.