While many countries have become ever more open and welcoming for foreign investment, the awareness of risks for national security stemming from or related to international investment has increased. Many governments have thus introduced policies that seek to protect their national security with the smallest possible impact on investment flows. Guidelines for recipient country investment policies relating to national security adopted at the OECD in 2009 provide recommendations for the design and implementation of such policies. This paper reviews commonalities and differences of policies implemented in 54 countries with a special focus on arrangements in 17 economies that have explicit policies in this area. It offers a comparative analysis of countries’ investment policy approaches to address national security concerns stemming from foreign investment; classifies the different forms of restrictions to address these concerns; identifies differences between restrictions on ownership and acquisitions; and presents how countries define the scope of application of their policies. The study also assesses how countries have implemented some of the key principles set out in the 2009 Guidelines in actual policy in order to meet their need to safeguard national security while reducing the impact of these policies on international investment.