Transnational marriages are increasing within the Asian region where one spouse migrates across national borders to marry. Compared with other forms of intermarriages, little is known about ethnic intermarriages involving transnational migration, especially in societies that are new immigrant destinations. Using social survey from South Korea (N = 64,972), this article examines the marital power dynamics between transnational couples and the well-being consequences of power differentials for the migrating spouse. The results suggest that upward social mobility obtained through transnational marriages, measured by dyadic gaps in education and family social standing between transnational couples, provides a solid foundation for many marital unions, and thus leads to marriage migrants’ better health, improved life satisfaction, and more positive views on transnational marriage migration. This article sheds light on the unique power dynamics of biethnic families, one of the emerging and unconventional forms of contemporary families, and informs policy makers across family, health, and migration domains.