The potency of a nation's security framework is increasingly dependent on the wholesomeness of its democratic structures, especially the legislature's ability to oversee the executive branch, including the security sector and intelligence agencies. This paper examined the role of legislative oversight as a catalyst for promoting Nigeria's national security within the context of a fragile regional security environment, pervading internal threats, and perennial governance dilemmas. The paper adopted an armchair research approach wherein relevant literature, constitutional, and statutory provisions were assembled and analyzed. The paper found that while the Constitution gives the legislature broad oversight mandates, including the power to approve security sector and defense budgets, confirm heads of security appointments, and conduct investigations and hearing but, their implementation remains impeded by several systemic impediments such as partisan considerations, limited technical expertise, inadequate access to security information, corruption, and absence of transparency. Moreover, instances of robust oversight, such as the 2014 legislative inquiry into the "Dasukigate scandal" regarding the misappropriation of the $2.1 billion allocated for arms purchases to fight Boko Haram, demonstrate a nascent but potent capacity to promote transparency, probity, and operational productivity within the security sector and intelligence community. The paper concluded that legislative oversight is key to effective national security strategies that protect life and property. This paper recommends the promotion of legislative independence and oversight responsibilities, improvement of the technical expertise of legislative committees, and institutionalization of a periodic reporting requirement that could transform oversight from a procedural formality into a strategic driver of national security.