Dissertation (MA International Relations)The study analyzed Illegal Migrant‟s Impacts on National Security using Dar es Salaam Region of Tanzania as a study area. Tanzania has been receiving migrants from Somalia and Ethiopia and beyond. Some of them have come to the country for the temporary stay while others have settled permanently in the country. While some have done so in accordance with the applicable laws, others have entered and settled in the country without following the applicable legal provisions. These are known as “illegal” migrants. A sample of 100 respondents was used and these were randomly Dar es Salaam region of Tanzania. The methods used in data collection are interviews, questionnaire, documentary review and focus group discussion. The statistical package for social science (SPSS) was used for management of data and analysis. In this study the theories pertaining to National Security was established to familiarize the reader with paradigms, frameworks and approaches in the field of national security. The study reveals that there is a weak security in the country borders, corruption and many porous routes which lead to the influx of illegal migrants in different regions of Tanzania. This has been due to the lack of funds and political willingness which contributes to the poor technology, inadequate number of workers and insufficient working equipment. The study recommends that in order to ensure that there is efficiency and sufficiency in securing country from illegal migrants there is a need to improve the commitment of the government and communities.