Abstract: For the past 3 decades, Africa is saddled with circumstances of armed conflicts of all kinds. Hence, socio-economic and political development of the continent becomes a complex task to actualize. Territorial borders of some member nations have become porous following wars that were fought. As a result, arms of all kinds are illegally transferred across the African borders, equipping either the rebels or government forces; on one hand to intensify armed hostilities in the continent. Equally, the arm trafficking provides ample opportunities for civilians to gain access to small and light weapons. This poses a great threat to contemporary African security. Therefore, the study examines the concerns of Millennium Development Goals with regard to the actualization of arms security in 21st century Africa. Methodologically, data for this study were gathered from secondary and primary sources. The design was based on the ex-post facto analysis. Hence, it is the findings that arms trafficking across the territorial borders of some African countries have affected the general security of the continent in such a way that economic stability, political advancement and social harmonization have remained complex task to be achieved by the Millennium Development Goals (MDGs). Accordingly, the study recommends that the United Nations should make the MDGs more practical oriented in order to capture the security crisis of developing countries, especially Africa that is faced with the enigma of arms trafficking across its territorial borders.