Militancy in the Niger Delta area of Nigeria is a problem that affects government, private organizations, and individuals. The government's Amnesty and Reconciliation Program encouraged individuals to denounce militancy in return for skills training and a monthly allowance. However, the amnesty program has not yielded the desired result of ending insurgent militancy. The purpose of this research was to better understand factors that cause individuals to join militant groups in the Niger Delta region, in order to proffer plausible solutions to address the causes of militancy. Using the root cause conceptual framework in this phenomenological research, I explored the causal factors of militancy in the Niger Delta region for an in-depth understanding of this phenomenon. The key research questions focused on the motivating factors that spur individuals to participate in militant terrorism in Nigeria's Niger Delta region and whether the implementation of the Amnesty and Reconciliation Program mitigated the problem of militant terrorism in Nigeria's Niger Delta. Data were collected from 10 individuals through in-depth face-to-face interviews, while concept mapping was applied in completing the analysis of interview data. Key results revealed 8 core areas as causes of militancy: the lack of local control of resources, underdevelopment, relocation of local government headquarters, poverty, marginalization, environmental pollution, education opportunities, and poor implementation of the amnesty program. Implications for positive social change include using the findings to develop more effective programs and policies for addressing the problem of militancy and to implement strategies that will reduce or eradicate militancy and associated problems.