The decreasing Korean population and shrinking workforce have resulted in a surge of foreigners entering the country to address labor shortages. This has led to an increasing demand for laws and regulations governing foreign workers in Korea, as well as a growing need for research on various aspects of immigration to address this complex issue. Using the 2018 National Multicultural Family Survey, this study examines determinants of immigrant workers’ wages in Korea, focusing on marriage and naturalized immigrants who are long-term settlers. Methods such as OLS regression, stratified analysis, and the Oaxaca-Blinder Decomposition are used in this research. I found that individual characteristics such as gender and country of origin strongly influence immigrants' wages. Especially with the gender variable, factors such as education, marital, and child-rearing status played significant roles, showing that they are facing issues similar to those of Korean workers, with women being notably disadvantaged. Furthermore, as these immigrants have assimilated into Korean culture, my findings suggest a need to address not only issues arising from immigration but also persistent challenges in the Korean labor market, such as gender wage differences and declining birth rates (0.7).