The paper addresses the security threat perception and securitization of existential threats in Lithuania. It focuses upon the securitization theory and its ability to explain the change of national security agendas as affected by the changes in national identity and existential security threats. It takes into account the internal and external factors that are shaping the objective and subjective national threat perception. The paper applies O. Waever’s securitization theory with an aim to explain how the national security threats are being addressed and perceived in Lithuania. Moreover, the paper is developed against the backdrop of the most recent developments in securitization theory and evolution of its theoretical perceptions of identity, existential threats, and legitimacy. It also discusses the possibility of inclusion of hybrid security threats into an analysis of securitization. The empirical part of the article assesses the most recent security challenges, provides evaluation of changes in national security perception, and portrays the dynamics of national security threats as defined in the National Security Strategies and the Military Doctrine. The paper focuses upon the most recent dynamics in security policy of Lithuania. It also takes into account the hybrid nature of security threats and the reaction to hybrid security elements such as: cyber security, information security, and international terrorism.