(MA International Relations)The study was designed to analyse illegal immigrants in Tanzania, this study aimed at analyzing challenges for Immigration and illegal immigrant in Zanzibar, The study used exploratory research approach where it explored, examined, and then provided the analysis of the data collected in the field. The study used questionnaire, interview and documentary review guides as tools of collecting data. Also it employed sample of 80 respondents to represent 350 employees of Zanzibar Immigration Department, this is equal to 23% of the total employees. Again the study was mainly conducted in Zanzibar and employed simple random sampling technique. The study discovered that, Zanzibar Immigration Department faces several challenges in dealing with illegal immigrants, Immigration Department has been given mandate to deal with illegal immigrant theoretically but not practically, Immigration law has weaknesses which need some amendment, also it lack resources to finish the problem of illegal immigrants. The study recommend that, Government of Tanzania should hasten the uses of National identity card which could help in the recognition of nationality, besides the amendment of Immigration policy was also recommended so as to fulfil the Government needs. Furthermore, also the amendment of Immigration act should put into consideration so as to bring about the target of finishing the problem of illegal immigrants.