Education for Sustainability (EfS) has been included in preschool teaching in several countries. Yet few studies investigate EfS in practice or the way learning environments affect teaching. This study investigates which learning environments and teaching strategies facilitate or, indeed, hinder EfS. An observational study was conducted at two preschools where the teaching and EfS practices of two teachers were observed both indoors, in the outdoor play area, and in the forest. Observations were analysed using qualitative content analysis and coded based on the teaching strategies and EfS practices in these three learning environments. An inductive analysis was then conducted to identify enablers and barriers for implementing EfS. Results show that planned teaching is the dominant teaching strategy indoors and in the forest but was absent in the outdoor play. Semi-spontaneous teaching was common in those learning environments that had been adapted to stimulate teaching. An enabler in the forest was movement in the place. In the outdoor play area, an adapted learning environment was an enabler just as it was indoors, where available teaching material was also an enabler for EfS. Barriers indoors were low expectations of children and the teacher’s supervisory role in the outdoor play area. In the forest, a strict teaching structure was a barrier for EfS. This study shows that it is useful for a variety of EfS practices to use different learning environments, indoors and outdoors, as well as different teaching strategies and that preschool teachers might need in-service training to overcome the identified barriers.