This study examined the influence of the high level of insecurity on the economic growth of Nigeria for the period 1999 to 2020. In a bid to actualize this objective it collected data from secondary sources such as the various editions of the Central Bank of Nigeria Statistical Bulletin. The data were analyzed using Augmented Dickey-Fuller (ADF) Unit Root test, Johansen co-integration test, and Error Correction Model. The selected variables (i.e. Gross domestic product, national terrorism index, militancy and ethno-religious conflicts) had a co-integrating relationship indicating long-run relationship among the variables. The result of the Error Correction Mechanism (ECM) had the expected negative sign and statistically significant at the 0.05 level, an indication that any disequilibrium in the system will be adjusted. Based on the conclusion made, it was recommended that government should solicit for correlated international assistance in the areas of sustainable economic growth, good governance, human rights protection, and environmental preservation plus promote the unity of the citizens along ethnic and religious lines. This would provide the enabling environment for people to work especially in the area of security of lives and property as no meaningful economic activity can thrive in the face of insecurity. Keywords: Insecurity, terrorism, militancy, ethno-religious conflict, economic growth.