This research is a qualitative study to determine the opinions of preschool teachers and pre-service teachers on environmental education and environmental awareness for sustainable development. The phenomenology approach, which focuses on individuals’ own experiences and the meaning of a phenomenon, was used in this direction. The study group of the research consisted of 68 preschool teachers and 72 pre-service preschool teachers. In the study, a semi-structured interview form consisting of open-ended questions was used as a data collection tool. The content analysis technique was used in the analysis of the data obtained from the interview form. According to the research results, it can be said that pre-service teachers have more theoretical knowledge than teachers and teachers have more practical knowledge than pre-service teachers. This can be explained by the fact that the knowledge that pre-service teachers obtain at university is quite new, they spend more limited time with children within the scope of applied courses, teachers communicate much more with children every day and they are more distant from theoretical knowledge. Furthermore, it can be said that teachers and pre-service teachers are sensitive towards environmental problems, interested in environmental education, willing and open to development.