Background: According to the Swedish curriculum teachers in all subjects have a responsibility to integrate a holistic perspective of sustainable development (SD) and teach according to an education for sustainable development (ESD) approach. However previous research has shown that teachers from different subjects perceive SD differently. Purpose: The study aimed at investigating if and how teachers' subject area influences their ability to implement a holistic perspective of ESD; we investigated both the impact of teaching traditions and the barriers that teachers experienced. Sample: A stratified sample of 224 Swedish upper secondary schools participated. An online questionnaire was sent and answered by a total of 3229 teachers at these schools. In total, there were 669 science teachers, 373 social science teachers, 483 language teachers, 713 vocational and esthetical-practical teachers, and 739 teachers from other disciplines who participated in the survey. Design and methods: The questionnaire consisted of questions requiring Likert-scale responses and multiple-choice questions. The data from the questionnaire were analyzed using Pearson's Chi-square test and one-way ANOVA. The significance level accepted was p less than 0.05. Results: Teachers were influenced by their own subject traditions. Science teachers in our study were grounded in the fact-based tradition and lectures were the most common teaching method used. The teaching tradition of the social science teachers seemed to be most in line to an ESD approach. Many language teachers (41%) stated they did not include SD issues in their teaching at all. Among the barriers identified, the most common obstacles were that the teachers lacked inspiring examples of how to include SD in their teaching and that they lacked the necessary expertise about SD. Conclusion: This study highlights the need for the management within schools to create opportunities for teachers to work collaboratively when teaching ESD. It is also important to provide further training that is adjusted to the needs of different disciplines. (Contains 2 tables, 4 figures and 1 note.)