Constitutionalism in South Asia reflects the complex interaction between democratic ideals, post-colonial state-building and socio-political realities. This research paper undertakes a comparative analysis of the Constitution of the Democratic Socialist Republic of Sri Lanka and the Constitution of the People’s Republic of Bangladesh, two constitutions shaped by colonial legacies, nationalist movements, and aspirations for social justice. Both constitutional frameworks aim to establish democratic governance, guarantee fundamental rights, and ensure the sovereignty of the people, yet they differ significantly in institutional design, treatment of religion, and constitutional amendment processes. The study adopts a doctrinal and comparative methodology, examining constitutional texts, amendments, judicial interpretations, and scholarly literature. It focuses on core constitutional principles such as popular sovereignty, separation of powers, fundamental rights, directive principles of state policy, and judicial review. Special emphasis is placed on the evolving role of the executive and judiciary in shaping constitutional governance in both countries.