Marine and coastal ecosystems are crucial in maintaining human livelihood, facilitating social development, and reducing climate change impacts. Studies have examined how the benefit perception of aquatic ecosystems, knowledge, and emotion about climate change affect peoples’ support for marine protection. However, their interaction effects remain understudied. The current study explores the intricate interaction effect of the benefit perception of aquatic ecosystems, knowledge, and worry about climate change on marine protection support. Bayesian Mindsponge Framework (BMF) analytics was employed on a dataset of 709 stakeholders from 42 countries generated by MaCoBioS—a research project funded by the European Commission Horizon 2020. The statistical analysis shows that the impacts of benefit perception of ocean ecosystems, knowledge, and worry about climate change on marine protection support vary due to their interactions. Specifically, when stakeholders perceive ocean ecosystems to have little utility in mitigating climate change, greater climate change knowledge and concern are associated with a higher level of marine protection support. Nevertheless, in the scenarios where stakeholders perceive the benefits of ocean ecosystems, the effect of climate change knowledge becomes conditional on the worry level. If stakeholders are concerned about climate change, those with a greater level of climate change knowledge will associate with a higher level of marine protection support. Otherwise, greater climate change knowledge will result in lower support. These findings highlight emotion’s importance in directing climate change knowledge’s effect on marine protection support. Linking people’s “objects of care” to the consequences of climate change can help improve climate change communication effectiveness.