This chapter examines the role of smart power in US digital public diplomacy toward Iran, focusing on the strategic use of both hard and soft power in adversarial relations. By revisiting key events surrounding the Iran nuclear threat, such as the Obama administration’s engagement with Iran and the 2015 nuclear agreement (JCPOA), and contrasting it with the hard-oriented public diplomacy under Trump, it explores how public diplomacy serves as a tool for conflict management and diplomacy in hostile contexts. Drawing on a constructivist perspective, the chapter proposes a model of adversarial public diplomacy, where the soft and hard elements of power are differentiated not by categorizing power resources as inherently soft or hard, but by the functions they serve in relation to three key actors. This approach highlights the dynamic, context-dependent nature of power in diplomatic engagements, offering a pathway to a more nuanced definition and measurement of smart power in foreign policy analysis.