This study explores whether patterns of doctorate attainment among Chinese and Korean international students in the USA have changed over time, both in terms of quantity (i.e., number of international students) and quality (i.e., the selectivity of the undergraduate and doctoral institutions), and whether these changes reflect the improvements in higher education sectors in China and South Korea. By analyzing data from the Survey of Earned Doctorates by the National Science Foundation in the USA, this study expands our understanding of the historical trends of transnational mobility as well as the link between the quality of students' undergraduate and doctoral institutions which goes beyond the US context. The study found that the number of doctorates from both China and South Korea consistently increased in the USA over four decades. However, while China continued to increase its proportional representations in the 2000s, South Korea experienced decreases in the proportional representations of US doctorates, from 12.2% in 1990s to 10.7% in the 2000s. This study also found that the quality of international students' undergraduate institutions is positively associated with the quality of doctoral institutions. In particular, the association between the selectivity of undergraduate and doctoral institutions among Korean doctoral graduates in engineering became stronger from the 1990s to the 2000s. By exploring the short- and long-term implications of quality improvements in higher education sectors in China and South Korea, the US higher education system will be better prepared for changes in the volume and quality of students that it receives.