This study explores the effects of spousal dissimilarity on marital stability among transnational couples in Korea. Utilizing micro-data from the 2009 Korean National Multi-culture Family Survey, this paper examines whether formation of transnational marriage generally involves positive assortative matching on age and education. Indices of age dissimilarity and educational dissimilarity are calculated for each country of origin of the foreign wife, and their relationships to the average duration of marriage are analyzed. This study also conducts a micro-level analysis of whether age and educational dissimilarity between spouses helps explain variations in marital duration and probability of getting divorced. Results show greater incidences of spousal dissimilarity in age and educational attainment among transnational couples, which supports the transnational openness hypothesis proposed in this paper. The extant hypothesis that spousal dissimilarity increases the risk of marital dissolution and shortens the duration of marriage is not found to fit transnational couples in Korea.