The integration of education for sustainable development (ESD) into all levels of education is a key priority in Kosovo's environmental action plan. However, at present it is not even known how environmental education (EE) is integrated in the country's educational system. With the help of a written questionnaire and in-depth interviews with 18 teachers, this study investigated the integration of EE in high schools (optional upper secondary education) in Kosovo. The representative sample of biology, geography, chemistry, and civic education teachers (244 persons) focused on various kinds of pollution and hazards of pollutants. Teachers' choice of topics was highly relevant, place-based, and linked to the experiences of students, but excluded sustainability issues such as the loss of biodiversity. EE was approached in three ways. The first approach critically reflected links between the natural, social, and cultural environment, while the second approach was characterized by knowledge submission of environmental facts. The third approach aimed at capacity-building and, in the sense of ESD, understood learning as process-oriented, participatory, and action-oriented. However, this approach was rather uncommon, most likely due to insufficient teacher preparation, large classes (up to 50 students), and little time (just one hour per week for EE). Class size and time also restricted outdoor activities, in particular field work. Nevertheless, in view of the interviewees, ideal EE would mean outdoor education, field work and other place-based, capacity-building practical experiences, and the development of critical thinking skills. This exemplifies that approaches to ESD may find support from dedicated teachers in Kosovo.