Immigrant flows in Greece after 1990 transformed Greece from a country of outwards migration to an inwards migration state. The contribution of immigrants in a globalized world of migration with sub-replacement fertility levels found in developed countries is a particularly interesting topic in demographic studies. The primary aim of this thesis is to discuss the changes of the demographic and socio-economic characteristics of immigrant population in Greece focusing on Albanian and Bulgarian immigrants. In order to answer these research questions, data from the last three national population census of 1991, 2001 and 2011 as well as vital statistics for European and non-European immigrants’ fertility in Greece have been used. The analysis is based on descriptive statistics for the differential age structure of Greek population and immigrant groups. Reasons for immigration to Greece, educational attainment of immigrants, rates of unemployment and employment status of immigrant population have been used to approach the research questions. The results indicated a younger age structure of Albanian and Bulgarian immigrant population. Meanwhile, immigrant population appears to have higher unemployment rates compared to native Greek population. Finally, a substantial decline of general fertility rates for non-European immigrant women in Greece compared to native Greek women has been observed within the years of the economic recession.