This paper examines the macroeconomic, political, and social ramifications of the Alliance of Sahel States’ (Burkina Faso, Niger, and Mali) exit from ECOWAS, portraying it as an institutional shock as opposed to a purely diplomatic split. It creates scenario-based insights into the expected transmission channels influencing trade, investment, fiscal stability, and governance using an integrated theoretical approach based on growth theory, Keynesian demand analysis, and regional integration frameworks. Despite limited sectoral resilience in sectors like mining and telecommunications, research indicates that withdrawal is likely to raise transaction costs, decrease investment flows, and erode regional economic stability, especially in already fragile and security-constrained nations. In summary, more institutional coordination and macroeconomic credibility are necessary for the region’s sustainable economic autonomy, underscoring the dangers of fragmentation in the absence of such frameworks.