This study presents a comparative content analysis of how teachers at eco-certified and teachers at non-eco-certified preschools in Sweden describe their education for sustainability (EfS). Sixteen teachers, eight from eco-certified preschools and eight from non-eco-certified preschools, were selected through a randomised sampling process. Semi-structured interviews were conducted, and the transcripts were analysed thematically, then comparatively. The thematic analysis generated four EfS practices: children's opportunity for agency, actively present teachers, children's experiences as a basis for learning, and communication between children and teachers and three teaching strategies: planned, semi-spontaneous, and spontaneous. These practices and strategies form the basis for a comparative quantitative and qualitative content analysis together with the three sustainability dimensions: economic, environmental, and social. In overall terms, the comparative quantitative content analysis shows only minor differences between the two teacher groups related to three aspects of their EfS. First, teachers at eco-certified preschools consider children's experiences in planned and semi-spontaneous teaching more often than teachers at non-eco-certified preschools. Second, teachers at eco-certified preschools create more adapted learning environments and materials to enable semi-spontaneous teaching, which lead to a more structured EfS with pluralistic elements is apparent among teachers at eco-certified preschools. These differences could be due to the profile of the preschools or the fact that they more often have relevant continuing professional education for teachers. Complementary studies are needed to demonstrate whether these differences are generalisable and to investigate the underlying causes.