The role of English as a Foreign Language in the educational context does not only aim to encourage students to become more communicative but also provide cultural knowledge because language and culture have an inseparable relationship. Accordingly, the ELT context should provide linguistic knowledge and nonlinguistic such as cultural knowledge. The present study aimed to investigate the presence of cultural information embodied in the Senior High School English textbook “Bahasa Inggris untuk kelas X”. Moreover, the current study also attempts to explain two in-service English teachers' perceptions of it. Document analysis, interviews, and classroom observation were used as data collection techniques. Drawing on Cortazzi & Jin’s cultural dimensions (1999) and Yuen’s cultural dimensions (2011) as the framework, the study attempts to examine cultural representation in a Senior High School English Textbook. The semi-structured interview session was conducted to explore the teachers’ responses toward the cultural material in the textbook. In addition, classroom observation was also conducted to explore to what extent the teachers utilize cultural material in the language classroom. The result displays that the dominant representation belongs to Indonesian culture, with products as the most cultural aspects that appeared. Although the teachers report that they had different perceptions of whose culture should dominantly exist in the textbook, they assume that practices cultural aspects should be represented more in the textbook to improve the student's attitude and behaviour. Moreover, the teachers show different strategies for conveying cultural material in teaching activities. Due to the significance of cultural knowledge for intercultural competence, this study has some suggestions for textbook writers and teachers. The textbook's authors should provide the various cultures from other countries to enrich the students' intercultural competence, and teachers should actively provide supplementary materials to support the material in the textbook.