Competitiveness has always been a multifaceted illusive concept, which has made it a real challenge for scholars and practitioners to find the most suitable measurement tools to completely encapsulate all the complex nuances of competitiveness. This becomes even more of a challenge when approached in relation to particular economic sectors. The agri-food sector is no exception, especially when considering all its interconnections with the other sectors: water, energy, transport, waste. All of them impact the achievement of the Sustainable Development Goals (SDGs). Similarly, scholars have been debating the meaning of sustainability for decades, some even arguing that it is a political, subjective, and, in some cases, self-contradictory concept. As far as the sustainability of agricultural competitiveness is concerned, the literature is still developing. It is much more focused on fostering environmental competitiveness, and less attention was paid to the strategies designed to capitalize on sustainable economic competitiveness—a concept that has attracted divergent opinions in the literature, mainly due to ambiguity. Thus, instead of falling into the pitfall of vagueness, this paper was aimed at bringing its contribution to this field by undertaking the research objective of exploring a single facet of sustainable agricultural competitiveness: the economic facet. Hence, this paper proposes the construction of the sustainable economic competitiveness index (SECI) with direct application for agri-food value chains. It consists of three attributes: (a) factor endowments, resource independence; (b) agricultural chain performance; and (c) national agricultural chain strategies and policies. In this study, SECI was tested against the cereal chain for a selection of EU countries, based on the data taken over from FAOSTAT and INTRACEN Trade Map, in the case of the 2011–2020 period. Various statistical and econometric methods were used to test the robustness of SECI. Results stand as proof that building sustainable agricultural economic competitiveness relies on a mix of strategic actions. The key vector in this mix is that trade flow patterns and policies must be calibrated in accordance with national factor endowments in order to achieve high levels of SECI. To add more managerial implications, this paper argues for the smart delivery of agri-food products with high added value instead of focusing on exporting big volumes of raw agricultural materials with little added value.