Nigeria's status and role as a regional power continues to impact the entire West African sub-region. However the country is facing serious security challenges that are complicated by transnational threats which are associated with organised crime and the activities of jihadist movements. Threats to security linked to the activities of illegal migrants, smugglers, drug traffickers and human traffickers in West Africa have attracted considerable attention from scholars, policy makers and practitioners alike. As the activities of the Jama'atu Ahlis Sunna Lidda'awati wal-Jihad (People Committed to the Propagation of the Prophet's Teachings and Jihad) also known as Boko Haram are spreading fast through the northern part of the country into a number of countries in West and Central Africa - notably Chad, Niger, and Cameroon - fears and anxiety have become more noticeable among stakeholders. Also, the challenge of piracy and maritime insecurity in the Gulf of Guinea threatens Nigeria's national security as well as regional stability. This study presents the role of Nigeria as a regional hegemon, and also discusses its response to transnational organised criminality and jihadist activities in the sub-region, highlighting Nigeria's official response as well as other interventions undertaken through bilateral and multilateral platforms. The study concludes that there is no controversy about the desirability of the Nigerian government to curb transnational organised crime and jihadist activities in the country. However, the complexities of strategies and modalities for effective curbing of transnational threats still requires in-depth and concerted efforts than have been given by stakeholders. One may argue that the prospects for effective control of cross-border crime in West Africa are positive. Both at bilateral and multilateral levels, Nigeria has shown commitment to working with other countries within the West African sub-region to address the menace of transnational criminality including smuggling, human trafficking and cross-border banditry. On the otherhand, the oversubscription of Nigeria and some of its immediate neighbours to pseudo-nationalist policies hinder the implementation of broad-based regional strategies to address transnational threats. Thus the general apathy and lack of courage in official circles and among civil society organizations and other non-state actors in West Africa to organise across national frontiers and engage in security and development discourse, all have the tendency to limit the prospects of effective control of transnational criminality. The efforts of the Nigerian government at combating transnational organised crime and the spread of jihadist activities are yielding somegains. However, lack of political will, bad governance, and poorly equipped and motivated defence and security agencies coupled with other problems such as the porosity of the borders and non-involvement of the people have continued to inhibit progress.