This paper examines how Education for Sustainable Development (ESD) is transmitted in the context of geography education by investigating the extent to which geography textbooks in Vietnam promote ESD principles. At the same time, the paper helps clarify how ESD is anchored in formal education and how ESD is contextualized in the specific context of Vietnam. This study involved a qualitative analysis supported by MAXQDA software (VERBI, Berlin, Germany), where geography textbooks from grade 6 to grade 12 in Vietnam were analysed to determine (1) how sustainable development (SD) issues are integrated into the content of the textbooks and (2) the extent to which questions and tasks in the textbooks promote competencies regarding the demands of ESD. The findings show that the textbooks somewhat promote ESD through their content and didactic approach. However, there are still some drawbacks. In terms of content, the textbooks’ main approaches to both SD content and geography core knowledge are description and indoctrination. In terms of their didactic approach, almost all questions/tasks ask students to memorize and reproduce information and rote learning rather than helping them promote ESD competencies. This reconfirms that ESD remains an add-on issue to an overcrowded curriculum, and the geography textbooks reflect an instrumental approach to ESD.