The chapter compares how the G20, the OECD and the IMF addressed fossil fuel subsidies and finds that while the three institutions agreed on the importance of reform of fossil fuel subsidies due to their environmental and economic consequences, they also differed in how they addressed these subsidies. Most notably, the IMF adopted a radical definition of fossil fuel subsidies based on the notion of corrective taxes, which stood out against the more established definition of the OECD. The chapter demonstrates that economisation may lead to diverging framings of the issue in economic terms. Subsequently, the chapter outlines how this divergence was driven by the differences in worldview, policy entrepreneurship and the degree of autonomy of the IO bureaucracy from principals. Yet, the similarities between their worldviews (they agreed on a range of fundamental issues), institutional interaction and overlapping memberships pulled in the direction of convergence between the institutions. Finally, there is a discussion on the consequences of this divergence at the international and domestic levels, while the convergence between the institutions was important for the attention to the issue and the norm of fossil fuel subsidy reform.