Cultism in Nigeria has evolved from its origins as campus confraternities in the 1950s into violent networks with a global reach. Initially established with social and ideological motives, these groups have transformed into transnational criminal organizations engaged in drug trafficking, cybercrime, human trafficking, and violent clashes both within Nigeria and abroad. Drawing on Social Disorganization Theory and the Transnational Criminality Framework, this study examines how institutional weakness, poor governance, poverty, insecurity, and migration facilitated the proliferation of cult gangs beyond Nigerian campuses into streets and diaspora communities. The findings reveal that Nigerian cult groups, such as Black Axe, Vikings, Eiye, and Maphites, now operate across Africa, Europe, Asia, and the Middle East, with recorded violent confrontations in countries like Italy, South Africa, Malaysia, and the UAE. National and international responses, including legislation, law enforcement crackdowns, community interventions, and immigration restrictions, have yielded limited success due to corruption, political patronage, weak enforcement, proliferation of small arms, and socioeconomic crises. These failures have allowed cult gangs to expand their criminal activities while undermining peace and security in both home and host countries. The study highlights profound implications for national development, including human capital loss, insecurity, diplomatic tensions, stereotyping of Nigerians abroad, and disruption of remittances. It concludes that cultism is not only a domestic security challenge but also a transnational threat requiring multifaceted responses. Strengthening governance, youth empowerment, institutional reforms, and international cooperation are essential to break the cycle of cult violence and mitigate its impact on Nigeria’s development.