The purpose of this study was to explore instructional designs for promoting inquiry practices in secondary school textbooks. Three criteria were employed to select the textbooks: (1) approved by the Ministry of Education in Singapore and the Ministry of Education and Culture in Indonesia, (2) used in secondary schools, and (3) included content and practices based on the current curriculum. Based on these criteria, six science textbooks from Singapore and three from Indonesia were selected for further coding in the dimensions of learning goals of inquiry skills, nature of scientific inquiry, and inquiry types. The results showed that more activities in both the Singaporean and Indonesian textbooks focus on observing and interpreting skills. However, few activities in the textbooks from either country provide an opportunity for students to engage nature of scientific inquiry. In addition, more activities in the Singaporean textbooks were designed as guided inquiry than those in the Indonesian textbooks. Finally, it is suggested that inquiry activities in textbooks should be revised to include nature of scientific inquiry, and more textbook analysis studies are needed to reveal characteristics of inquiry activities in textbooks for different subjects.