Over the past decade (2014–2024), Nigeria has experienced a significant rise in youth and skilled professional emigration, widely known as the Japa Syndrome. This mass migration, driven by economic hardship, insecurity, unemployment, and the decline in public services, has had a profound impact on the nation's socio-economic development. This study adopts a mixed methods approach, combining secondary data analysis with qualitative content review of policy documents, media reports, migration statistics, and academic literature as well as some oral histories. Key sectors such as healthcare, education, and innovation are examined to assess the short- and long-term consequences of brain drain. Findings indicate that while remittances from the Nigerian diaspora contribute to foreign exchange inflows, they do not compensate for the loss of skilled labour and weakened domestic productivity. The paper concludes by proposing strategic, evidence-based policy recommendations aimed at reversing the migration trend through systemic reform, diaspora engagement, and sustainable youth empowerment. The study underscores the urgent need for a coordinated national response to mitigate the adverse effects of the Japa Syndrome on Nigeria's development trajectory.