Uncontrolled migration is one of the threats to the state, and as illegal immigration, it is a leading threat to international security. From the point of view of state security, illegal immigration is classified as “requiring caution.” In the case of Poland, illegal immigration is to a considerable extent handled by organised crime of transnational reach, effectively taking the form of criminal enterprises. In the present day, differentiating between migration and exile is intricate, because the reasons behind migration are unclear and depend on numerous factors, also related to migration policies in target countries. However, for criminal enterprises, which stop at nothing to maximise their business profits, both refugees seeking refuge and migrants seeking to improve their socio-economic situation are a source of substantial fi nancial gain. Criminal organisations generate profi t by committing various crimes. This article also looks at international and national institutions combating illegal migration as a threat to the security of the Republic of Poland and Europe. 1. Article was based on the scientifi c co-operation between authors during preparation of their master thesis, Piertuniak M., Master Thesis: Impact of Illegal Immigration on State Security of the Republic of Poland (Wpływ nielegalnej migracji na bezpieczeństwo Rzczypospolitej Polskiej) , National Security Faculty of War Studies University, Warsaw 2018.