This research examines how Cold War science diplomacy facilitated the dissemination of American secondary science curricula in Japan during the 1960s, focusing on the interactions between U.S. and Japanese scientists. The Physical Science Study Committee (PSSC) and Biological Science Curriculum Study (BSCS) were part of U.S. diplomatic efforts to promote the superiority of freedom and democracy among allied nations. While previous studies emphasize a donor-recipient dynamic shaped by American strategies, this research shifts the focus to the contributions and collaborative efforts of scientists from both countries in the implementation of the new curricula. By tracing the exchange of ideas and practices between scientists — including the translation and revision of textbooks, the screening and adaptation of educational films, and the importation and production of experimental kits — this study provides insights into the intersections of Cold War diplomacy, the formation of scientific knowledge, and the political dimensions of science education.