Dissertation (MA International Relations)The dissertation aims at the assessment of the impacts of illegal immigrants on the national security in Tanzania. The dissertation attempts to examine the impacts of illegal immigration and its associated threats. The specific objectives aimed to identify the nature and the types of illegal immigrants threats the security, the kinds of security threats illegal immigrants cause. Methods of data collection were interviews, questionnaire, and documentary review of relevant documents. A total of 80 respondents were interviewed, including immigration officers, police officers, immigration police and communities. Data collected were analyzed by a computer programme (Statistical Package for Social Scientist (SPSS) Version 16. The study was conducted in the Dar es Salaam city which is located on the East Africa Coast because the city is the center of commerce, industries and trade and also major outlet to other parts of East and Central Africa. Such activities contribute to the growth of the city and bring in many people for business purpose. The sample selected from the population using purposive and stratified sampling. The basic approach used to collect data was through questionnaire which involved structured questions. The questionnaires were administered to the respondents by personal delivery mode of distribution. The findings showed that the country security is still in danger due to the several threats posed by illegal immigrants including increasing crimes, drug smuggling and other criminal activities. Also lack of national identity reported to challenge the national security. Therefore the researcher proposed the solutions that, increasing number of police in country borders and enforcing laws should be emphasized in order to minimize the number of illegal immigrant crossing country borders.