Human migration in the world is an old and on-going phenomenon. Humans move from place to place across local and international boundaries for various reasons. International migration requires documentation such as visas, passports, resident and work permits that are required for one to legally migrate to, and settle in an area. However, there are people who enter countries without documentation, and such people are referred to as undocumented migrants. This research investigates undocumented immigration in Zambia, with reference to Lusaka City. The theoretical framework that underpinned the research comprised four theories of international migration. These were the neoclassical economics theory of migration, new economics of labour migration theory, dual labour market theory of migration, and Kunz’s refugee migration theory. This researcher adopted the intensive research design and used the case study method, where Lusaka City (Zambia) constituted the case study area. The researcher gathered primary data from the Lusaka City Council, the Zambian immigration department headquarters, and from the informal settlements of Chibolya, Mandevu and Matero. Questionnaires were administered to the sampled immigration officers and Lusaka City Council officers, and interviews were conducted with Zambians and undocumented immigrants in the informal settlements. The research findings showed that undocumented immigrant interviewees came from the Common Market for Eastern and Southern Africa (COMESA) region. The undocumented immigrant interviewees entered Zambia due to the peace and economic opportunities found in the country, as well as joining their relatives, spouses and friends who were already in Zambia. Once in Zambia, the undocumented immigrant interviewees migrated to Lusaka City mainly for economic reasons. The major economic activity that undocumented immigrant interviewees were engaged in, was trade. Others were employed in the informal sector. Cooperation and complaints (challenges) characterised the co-existence between the interviewed Zambians and undocumented immigrants. Furthermore, undocumented immigrants in the case study areas brought about socio-economic and cultural benefits to the Zambians. Undocumented immigrants also contributed to socio-economic and environmental challenges in the case study areas. The Zambian government worked towards addressing the challenges of undocumented immigration in Lusaka City and above all, reducing the phenomenon. Much literature and research on undocumented immigration focussed on the phenomenon at the national level, and not the local urban spatial scales. The research therefore aimed at investigating undocumented immigration in Zambia with specific reference to the urban locality of Lusaka City / Geography / M. Sc. (Geography)