This chapter argues that public diplomacy practitioners must adopt a new culture of expertise grounded in empirical evidence, rigorous evaluation, and adaptive learning. Expertise requires two essential conditions: clear feedback and deliberate integration of that feedback through effortful practice. Yet public diplomacy often lacks these feedback loops, leading to overconfidence and ineffective programming. Through a case study of a public diplomacy campaign that inadvertently exacerbated political violence, the chapter highlights the risks of relying on anecdotal evidence rather than systematic evaluation. It proposes a new framework for expert public diplomacy emphasizing: (1) clearly articulated, research-informed goals; (2) robust monitoring and evaluation systems; (3) iterative learning loops to refine strategies; and (4) a workforce trained in analytical and evaluative competencies. Ultimately, it calls for institutional reforms to embed evaluative rigor and intellectual humility—namely, individual expertise—across the diplomatic enterprise, ensuring that public diplomacy is effective and accountable in an increasingly complex global environment.