My dissertation examines Japanese and American intellectual discourses, including discourses by Christian leaders, on the topic of Japanese transpacific migrations, and sets such discourses in conjunction with related Japanese migrant practices from the beginning of the twentieth century through World War II. I focus on how both Japanese and American intellectual discourses with regard to Japanese migration reflected keen interest in the integration of heterogeneous populations in both empires. In particular, I analyze the emphasis in these discourses on the multi-ethnic/racial character of the intellectuals' own nations and consider Japanese migrants' responses to such discourses. I argue that the Japanese transpacific migration is an important historical factor in the development of discourses on the broader nation formation in the twentieth century. My study bridges the fields of Japanese studies and American studies and reveals new points at which transnational studies of Japanese migrations and comparative studies of racism in the Japanese and American empires converge. Overall, my study illuminates not only the parallel mechanisms of Japanese and American imperial nation formations but also the role of transpacific Japanese migration as an important site of interaction between the two countries. Such an analysis has not, to the best of my knowledge, been undertaken in either Japanese studies or American studies. Thus, my thesis offers new perspectives on existing nationalized disciplines and articulates the critical potential of transpacific studies.