The rise in crime and insecurity across West Africa and the Sahel has led to the expansion of several regional Non-State Armed Groups (NSAGs). In Nigeria, particularly, the sense of low performance by the security forces has further caused an increase of Community-Based Armed Groups (CBAGs), who have become a fixture in the national security landscape. These CBAGs present a complex challenge to communities, governments, development implementers, and security providers. One of these CBAGs is the Vigilante Groups which are operational at the local and state level. Despite being prohibited by the Constitution of the Federal Republic of Nigeria, armed vigilante groups carry out law enforcement activities in an ever-growing number of states and communities with the tacit, and sometimes explicit, endorsement from the state governments and local authorities. Vigilante Groups have become a double-edged sword: though they provide an apparent needed localized security, they also undermine central authority, violate human rights and commit sporadic violence. Elucidating this ambiguous characteristic of vigilante groups as alternative security sources in Nigeria is the main focus of this paper. We argue that vigilante groups cannot represent a robust and sustained security source due to inadequate security training and the absence of an acclaimed authority, which are inherent characteristics to these groups. This paper utilizes both primary and secondary sources of data collection to arrive at the conclusion that the failure of the federal authorities to both contain and control vigilante groups will further deteriorate and/or disintegrate the internal security apparatus and social fabrics/cohesion of the Nigerian society.