If we intend to successfully integrate Education for Sustainable Development (ESD) in the general educational programs, it is important to utilize available methods and resources. This paper argues that English Language Learning textbooks in Iran have the potential to be useful resources and a viable springboard for the implementation of ESD. For this purpose, the present study explores the content of English textbook series developed by Iranian authors through the lenses of ESD. The framework for analysis was based on UNESCO's Earth Charter and the Roadmap for Implementing the Global Action Program on ESD. The findings reveal that the themes of sustainability are present in these English textbooks to a good extent. However, the results suggest that there must be a more even distribution of such themes throughout the series. Also, the role of the teacher as a facilitator in developing discussions around such themes is highlighted.