Immigration has social, political, economic, and security significance in Sri Lanka. Immigrants bring economic potential to the countries receiving them but also pose many security threats that may include criminal, terrorist, and extremist activities, as well as ethnic tensions and sectarian violence. This study identifies some of the potential threats posed by immigration, both legal and illegal, and examines the underdeveloped framework of Sri Lankan immigration law. A comparative analysis of Sri Lanka, its neighbor India, and the island nation of Bahamas serves to identify possible measures for revising the existing counterterrorism approaches and introducing new strategies to Sri Lanka. Furthermore, an analysis of these countries demonstrates that reform of comprehensive policies, the practice of immigration control, and effectively coordinated counterterrorism strategies to monitor immigrants may enhance the national security of Sri Lanka.