Single organizations encounter intricate challenges in meeting the UN’s Sustainable Development Goals (SDGs) on their own and thus are increasingly concerned with forming ecosystems. This is also the case in the e-commerce domain. It is assumed that particularly focal actors of such ecosystems have the power to foster initiatives towards more sustainability. We conducted an embedded multi-case study with 135 initiatives collected from three types of e-commerce ecosystems to uncover what sustainability goals are addressed by different ecosystem participants. This paper’s analysis explores (1) what sustainability initiatives are reported from focal actors and differences depending on a specific type of ecosystem, (2) dependencies between SDGs within the initiatives, and (3) the degree of involvement of other ecosystem actors and how they contribute to certain SDGs. Our work synthesizes existing initiatives towards sustainable development to give orientation and impulses for practice and academia as well as outlines avenues for future research at the intersection of ecosystems and sustainability.