The growing relevance of data-driven technologies in children’s everyday lives highlights the need to introduce fundamental data literacy concepts in primary education. To achieve this, primary school teachers must possess adequate data skills and know how to teach them effectively. A Massive Open Online Course (MOOC) was therefore developed to provide (prospective) primary school teachers with essential data literacy competencies, covering basic concepts, data evaluation and security, and introductory machine learning, complemented by ready-to-use teaching materials. Preliminary results from an ongoing evaluation show that participants are highly motivated, consider data literacy important for both their personal and professional lives, and generally rate their prior knowledge as moderate. Despite this, most feel capable of conveying data literacy after completing the course. These findings suggest that a MOOC is a suitable way to integrate data literacy into teacher education and to support its implementation in primary school classrooms.