This paper compares the impact of traditional and non-traditional security threats to the national security of Croatia and Serbia by analyzing the National Security Strategies. The security concept is constantly changing due to the globalization of the world and the development of national and international security. Regardless of the fact that today’s security is largely affected by non-traditional threats, such as terrorism, irregular migration and transnational organized crime, which are addressed throughout the paper, there are still chances of armed conflict. All countries invest in creating a strong national defense that can respond to the mentioned threats. The goal of the research is to show how similar, or different, two states located in the same regional environment are, and how they are affected by and deal with these threats. Although this paper mostly focuses on comparing the Strategies of the two countries, relevant laws and documents dealing with the analysis of the impact of non-traditional threats today are also mentioned. By comparing the National Security Strategies of Serbia in 2009 and 2019, it can be seen that there are minimal differences in the understanding and relation towards security threats, the same as in the Croatian strategies, regardless of the constant changes in the security environment. A comparative analysis of documents concludes that Croatia and Serbia face traditional and non-traditional threats to national security almost equally, but the difference can be seen in the impact of terrorism, irregular migration and transnational organized crime today.