World economic crises, internal economic and political instability have led to declining the level of investment attractiveness and investment security of Ukraine. The aim of the article is to propose an integral index in order to assess investment environment security and determine factors affecting the investment environment security of Ukraine. The suggested assessment is based on the data of World Bank’s indexes with the following blocks of factors: the availability of economic freedom, favorable organizational conditions for doing business, political and legal freedom, supply of resources and infrastructure development. The assessment of Ukrainian investment environment security and its Western neighbors – the European Union member states – has shown that it has lowest rank and highest volatility in Ukraine. The article identifies a direct statistical relation between the volume of foreign direct investment flows in Ukraine and the indicator of political stability and the absence of violence in the country. The main reasons of investment attractiveness reduction in Ukraine were as follows: conservative attitude of investors towards risks due to political instability, manifestations of violence and terrorism; deterioration of the overall financial situation of enterprises, which are the recipients of investments. The article substantiates that conditions for the investment attraction and secure environment in Ukraine have not been formed yet. The system of indicators and criteria for assessing the level of investment environment security should be expanded.