As Europe faces the twin imperatives of decarbonization and strategic autonomy, nuclear energy has re-emerged as a critical component of the continent’s energy and security architecture. Romania offers a compelling case study of how a mid-sized country can leverage its nuclear program not only to support climate goals, but to reinforce regional resilience and exert regulatory influence. This article examines the evolution of Romania’s nuclear diplomacy focusing on the transformation of its regulatory authority National Commission for Nuclear Activities Control (CNCAN) into a platform of soft power, regional cooperation, and technical leadership. By integrating emergency preparedness systems, piloting the deployment of small modular reactors (SMRs), and anchoring European safety standards in the Black Sea region, Romania contributes to a new paradigm where nuclear regulation becomes a geopolitical asset. The Romanian example illustrates how technical competence and regulatory trust can serve broader goals of energy transition, strategic credibility, and cross-border stability.