This study aimed to explore how the indigenous (national) culture of teaching and learning mediates teachers’ understandings of constructivism in China and the U.S. Thirty middle school math teachers who are self-identified with the mathematics teaching reform movement in each country participated in this study (NCTM 2000 Math Standards in the United States or the MOE 2001 Math Standards in China). Both theoretical and empirical methods were adopted for this research. Theoretical analysis led to a new cultural model that helped select appropriate cultural elements for this study. Based on emergence theory, the new model perceives Confucianism and Taoism as the most influential beliefs and values in terms of teaching and learning in China, in contrast with Behaviorism and Individualism in the U.S. This study revealed that the indigenous culture of China and U.S. greatly influenced teachers’ understandings of teaching and learning.