The aim of this qualitative study is to take a closer look at how certified preschool teachers integrate sustainable development in their daily work with children, and to gain a perspective into the teachers’ level of awareness regarding sustainable development. Drawing from a sociocultural perspective with elements of holistic learning methods, the present study is focused on interviews conducted by e-mail with preschool teachers from two different preschools located in suburban Stockholm. One of these preschools works more with sustainable development than the other, being enrolled in the Grön Flagg programme. The results from the semi structured interviews show that there are subtle differences in how teachers at the two preschools view and work with sustainable development. Teachers from the Grön Flagg preschool have more knowledge when it comes to integrating sustainable development. However, further studies are needed to gain a broader view into how preschool teachers gain this knowledge, whether it be in their workplaces or somewhere else. This study shows that working in a preschool that focuses on sustainability could generally increase teachers’ knowledge of and interest in sustainable development in their work with children.