There is a long history of debate on which Market-based Mechanism (MBM) should international shipping adopt to reduce carbon dioxide (CO2) emissions. However, literature presents differing preferences for a suitable MBM for international shipping. There are those who support a carbon tax, those who support an ETS, and those who remain on the fence. Hence, this study aims to find out: which MBM is suitable to reduce CO2 emissions for international shipping?