Green Budgeting is an important new tool for managing environmental performance in public organizations. Despite its growing popularity in recent years, particularly in Europe, few studies have focused on this tool in the field of administrative sciences. What is more, the term ‘Green Budgeting’ tends to cover a wide variety of practices in public organizations. In response to the current limitations of the academic literature, and to clarify the concept of Green Budgeting, our article examines the challenges of Green Budgeting and the choices that public organizations make when implementing this approach. Based on a literature review, two case studies, expert interviews and our participation in various Green Budgeting think-tank events, we identify and discuss three challenges arising from the design and one challenge arising from the use of this new environmental performance monitoring tool, and propose a framework for analysing promising Green Budgeting initiatives with a view to future research.