Emissions from shipping have consequences for human health and climate change, yet achieving policy change to reduce these emissions remains challenging on a global scale. The International Maritime Organization (IMO), the UN Agency tasked with formal international policy-making for the maritime sector, stands at the center of a complex maritime governance architecture. Yet, it is often criticized for heavy industry influence and power concentrated in the hands of a few actors. There has been recent research supporting this, while other research suggests that there are new actors influencing the agenda on shipping emissions. This article examines if the increasingly multi-actor and multi-layered governance architecture in shipping means that the actors and power in the IMO have shifted as well. The data were compiled from a selected sampling of the IMO documents from the Marine Environmental Protection Committee (MEPC) meetings between 1988 and 2021. The paper follows the agenda item of focus, ‘Air Pollution’, as it evolves over time and identifies actors utilizing three indicators of influence, submissions to the MEPC, the ISWG-GHG, and the delegations at the MEPC meetings. The research shows that some of the early state actors on this issue are still highly active (Norway, Japan, US), while other actors emerge over time (China, Marshall Islands). The emergence of the NGO Clean Shipping Coalition is notable, as is the complex role of the European Commission. Industry associations and flag states maintain active roles, yet the changes noted suggest they do not have the same influence they once did over emissions issues in the IMO.