In July 2023, the International Maritime Organization (IMO) adopted its 2023 Greenhouse Gas (GHG) Strategy, establishing a pathway for decarbonizing the shipping sector by around 2050. The 2023 strategy followed a series of unilateral measures undertaken by the European Union (EU), as part of its European Green Deal, which overlapped with the IMO’s climate jurisdiction. Considering the EU’s climate leadership ambition and its track record of uploading environmental legislation into the IMO, it would appear very likely that the European Green Deal influenced the negotiations of the 2023 IMO GHG Strategy. Yet, competing perspectives in the literature cast into debate how and to what extent the EU would have done so. This paper therefore answers the research question: How did the EU’s inclusion of shipping related provisions within Fit for 55 influence the negotiations on a revised IMO GHG reduction strategy? Data is based on a triangulation of participant observation at MEPC 80, semi-structured interviews with EU and non-EU negotiators at the IMO, and official documents. It finds that the adoption of Fit for 55 triggered a causal mechanism that ultimately led to the EU influencing the 2023 IMO GHG Strategy negotiations within a logic of interplay by commitment. The legislation created a dynamic in which the EU was able to work as a bloc within the IMO on climate issues for the first time, giving it clout as a bloc of 27 IMO member states which could therefore push for its objectives in the negotiations. However, the actual extent to which it influenced the substance of the strategy is up for debate, thereby nuancing the relevance of EU legislation and standards within this important, yet often overlooked international organization. The findings carry important implications for our understanding of the European Green Deal and its external consequences.