Illegal migration is a global phenomenon that has affected the International community and relations among nations. Migration is the movement of people from place to place and has existed since the history of Man. Migration is also a means of economic survival and of power struggle. It becomes illegal when people enter other countries without permission. Illegal migration, therefore, means the movement of persons from their own country to another nation across the borders through ways that are in violation of the destination country’s immigration rules. This has been on the rise in recent times particularly among migrants from sub-Saharan Africa, to more developed countries in the West and from research Nigerians make up a large proportion of these undocumented migrants. The rising number of these undocumented immigrants has impacted significantly on international relations worldwide and has made the issue of migration a major concern in international relations and international law. The study relied on secondary data and reviewed extensively literature on the subject and analyzed it using content analytical approach. From the analysis, the study revealed that illegal migration particularly from Africa greatly influenced US foreign policy on migration in recent times. Given the zero tolerance policy on illegal migration by US, the study recommends amongst others that Safe and legal migration avenues should be established and extended to illegal migrants and refugees resettled in receiving countries. Again, there should be renewed cooperation between the receiving countries and source countries so that adequate help and succour can be provided to illegal migrants who voluntarily return.