The migration waves provoke many challenges and risks regarding the states’ security including that of the Republic of Moldova. Illegal migration has often resulted in the traffic of human beings, arms and drugs. An internal and external migration has recently become a specific phenomenon for the Republic of Moldova, bringing up the demographic, social, cultural and economic consequences. The migration process analyzed in the illegal light can be characterized through many factors, such as: illegal border crossing using the different ways and methods, illegal staying in the country, illegal working abroad… This paper analyzes an illegal migration as the main threat to the Republic of Moldova’s security. At the same time the authors point out the importance of main factors promoting the illegal migration.