The United Nations (UN) is mandated to maintain international peace and security. The UN attempts to achieve this mandate through different means including peacekeeping by deploying personnel and experts in conflict situations. The UN has adopted number of policies and mechanism to strengthen its peacekeeping operations. Although there are number of activities focusing on peacekeeping with notable successful operations, the UN still face issues and challenges which have been negatively influencing the efficiency, effectiveness and the success of its peacekeeping operations. This paper has attempted to examine the key activities of UN peacekeeping operations, their impact, and the major issues that negatively influence and challenge the peacekeeping operations. The study has found that the UN peacekeeping operations have worked effectively in managing conflict situations and establishing peace in many parts of the world. However, the shortcomings and issues particularly in terms of political, military and humanitarian aspects of the operations have negatively influenced the peacekeeping operations in achieving their targets successfully. The study urges the importance of policy and institutional reforms together with commitments of parties, institutions, and involving actors in order to strengthen peacekeeping operations and establish sustainable peace in many corners in the world.