The maritime shipping sector is one of the hard-to-abate sectors in need of policy guidance for enabling sustainability transitions. Through the lens of policy mix characteristics, specifically consistency and comprehensiveness, we analyse the development of the global policy mix, implemented by the International Maritime Organisation, for reducing ship emissions, and its technology implications regarding ship-owners’ choice of propulsion technology. We elaborate on conceptualisations of policy mix consistency and comprehensiveness, which allow for an improved understanding of the role of policy in transition processes. Our empirical analysis indicates that although the sector has one main regulator, the overall policy mix lacks consistency and comprehensiveness, as the implemented instruments are insufficient to achieve set emission reduction targets. Furthermore, the design of the regulatory framework creates a technological lock-in on fossil fuels and there are insufficient incentives for ship-owners to invest in sustainable technology.