Textbooks are an essential source for the implementation of new curriculum in many countries. However, the role of textbooks in the process is not a fixed entity, as it is shaped by individual teachers' practices. This study aims to investigate, through the lens of teachers' views, what role textbooks play in the implementation of curriculum development in two educational settings, Shanghai, China and Central Java, Indonesia. Using a mixed-methods approach, including surveys and interviews, to collect data from 84 mathematics teachers in both countries, the study examined the interplay between curriculum development with a focus on three dimensions -- teaching strategies, content, and assessment -- and the role of textbooks in its implementation. The results showed that overall textbooks play an important role in the implementation of curriculum development in both Chinese and Indonesian educational settings, but differences were also found about the role of textbooks in different dimensions of the implementation; while Chinese teachers view the content of teaching, Indonesian teachers chose teaching strategies as the most important aspects of textbooks in implementing new curriculum, and the differences are related to the fact that curriculum reform in each country has different characteristics, and in particular, Indonesian teachers are more encouraged to construct their content according to the needs of their students, allowing for differentiated learning, which contributes to the discretionary use of textbooks by both teachers and students. The paper argues that these characteristics should be supported by textbooks that are aligned with curriculum reform in different educational settings.