The changing nature of twenty-first-century security threats has exposed the limitations of traditional state-centric approaches that prioritize military operations and territorial defense while overlooking the socioeconomic and governance factors that drive insecurity. Nigeria exemplifies this challenge, as substantial investments in defense and internal security have achieved only limited success in addressing persistent threats such as terrorism, banditry, kidnapping, farmer-herder conflicts, separatist agitations, cybercrime, organized crime, poverty, unemployment, and climate-related displacement. These interconnected challenges continue to undermine national stability, economic growth, democratic governance, and citizens' well-being, highlighting the need to shift from an operational security model to a human security approach. This study examines the transition from conventional security operations to a human security framework as a strategy for achieving sustainable peace and development in Nigeria. Guided by Human Security Theory, Securitization Theory, Human Development Theory, and Systems Theory, the study adopts a qualitative methodology based on documentary analysis and comparative institutional review of government policies, scholarly literature, and reports from international organizations. It argues that lasting national security requires addressing the structural causes of insecurity, including poverty, inequality, weak governance, corruption, environmental degradation, food insecurity, unemployment, and social exclusion, rather than relying solely on military responses. The findings reveal that Nigeria's security architecture remains highly centralized, reactive, and militarized, with weak institutional coordination, inadequate intelligence integration, limited community participation, and insufficient accountability undermining its effectiveness. To address these shortcomings, the study proposes an Integrated Human Security Architecture for Nigeria (IHSA-N) that integrates defense, intelligence, policing, economic development, environmental sustainability, public health, digital governance, social protection, and community resilience into a unified security framework. The model emphasizes preventive security, inclusive governance, inter-agency collaboration, and citizen participation as essential pillars of national stability. The study concludes that adopting a human security approach would strengthen state legitimacy, promote sustainable peace and economic development, and support the achievement of the Sustainable Development Goals (SDGs) and the African Union's Agenda 2063 through comprehensive institutional reforms and people-centered security policies. Keywords: Human Security; National Security; Security Architecture; Sustainable Peace; Sustainable Development; Nigeria; Security Governance; Human Development; Conflict Prevention; Public Policy.