Over the past few decades, the volume of international migrants has increased considerably. As a result, impacts of international migration on migrants' communities of origin have become much more prevalent and diverse. Using both quantitative and qualitative methods, this dissertation investigates a little studied aspect of such diverse impacts: the impact upon ethnic structures and relations in migrants' communities of origin. More specifically, I examine to what extent international migration affects the level of socioeconomic inequality across ethnic groups and how such impacts influence indigenous people's ethnic identity in two Central American countries: Guatemala and Nicaragua. I contend that ethnic identity shift is one of the most significant changes that international migration brings to these countries because such a shift can even endanger the existence of the indigenous population. I have found that international migration reinforces ethnic identity shift from indigenous to Mestizo in both countries. At the same time, the pace of such a shift differs by a community's characteristics including its demographic composition and definition of indigenousness. While it is hard to deny the fact that international migration provides indigenous people in both countries economic opportunities that are hard to obtain through other ways, it can also have unexpectedly negative effects on ethnic minorities and their cultures in the long run. Since indigenous people in both countries face a tough economic reality, it is difficult to prevent them from migrating to other countries. In such a situation, to conserve indigenous cultures and prevent more indigenous people from abandoning their ethnic identities, we need to assure that indigenous people can feel pride in their cultures while they participate in national economy and politics under the strong pressure caused by changes originating from international migration and multicultural reforms. Understanding how the definition of indigenousness is constructed and transformed as well as a mechanism of ethnic identity shift is an essential step to finding solutions to the dilemma related to international migration among indigenous people and achieving a robust multicultural society. / text