This paper reports on research concerning Greek in-service Primary teachers' perceptions about environmental issues and attitudes towards Education for Sustainable Development. A questionnaire with multiple-choice and open-ended questions was used in order to gain more comprehensive understanding of their thoughts. The analysis of data revealed that teachers hold misunderstandings or misconceptions of the conceptual meaning of the terms "sustainability" and "renewable source of energy." Furthermore, the implementation rate of environmental programs in schools is relatively low considering teachers' interest in the issues. This is due to lack of familiarity with new methodological approaches which promote environmental matters. By taking into account these research findings, possible implications arising from supporting teachers to implement environmental programs in schools are discussed and suggestions for overcoming the outlined difficulties are made.