Children are a particularly vulnerable group and, in northeast Nigeria, they are severely affected by Boko Haram terrorism. Although previous studies have looked at the effects of terrorism on children’s mental health, there is a lack of peer-reviewed studies on the effects of terrorism on adolescents’ psychosocial adjustment. This study addresses this gap with data on the consequences of Boko Haram terrorism in the northeast of Nigeria. A cross-sectional research design was adopted through systematic sampling. In total, 391 children who were directly affected by Boko Haram terrorism were surveyed. A majority of the sample was male (60.4%). Respondent age ranged from 11 to 23 years (M = 18.00, SD = 2.83). Analyses revealed that 291 (74.42%) of the respondents reported severe traumatic exposure—a markedly increased percentage compared with prevalence rates in countries without conflict. The majority of respondents (70.4%) reported clinically significant symptoms of post-traumatic stress disorder (PTSD). PTSD regularly co-occurred with other mental health and behavioral symptoms: depression, anxiety, and aggression. Terrorism-induced distress had an adverse effect on psychosocial adjustment (R²= .364, F(6, 385) p < .01). For example, it was found that children were restricted in their social life. Boko Haram terrorism has a devastating impact on adolescents’ mental health; most victims presented clinically relevant symptoms of PTSD. The victimized respondents were affected in their psychosocial adjustment to daily life and their educational development. Their vulnerability increases the risk of becoming potential recruits for terrorists. Supporting the victims would thus not only reduce their suffering but also decrease the likelihood of an ongoing cycle of violence.