The world’s oceans are warming. Coastal oceans experience more notable warming than open oceans, which is considered to have severe impacts on coastal marine ecosystems. The Eastern China Seas (ECSs) have one of the widest continental shelves in the world and have been subject to climate warming over the last century. The cross-shelf and air-sea heat exchanges are the two major processes that dominate the heat budget changes of the ECSs, but research is still lacking. In this study, the current and future changes in the cross-shelf and air-sea heat exchanges are discussed, and their relative contributions to the heat budget changes of the ECSs are quantified using an atmosphere-ocean coupled model system. Results show that the recent and future ocean warming in the ECSs is linked overall to cross-shelf heat transport. However, the air-sea heat exchange can significantly reduce the warming of the ECSs. The relative contribution is projected to increase for the Taiwan Strait and decline for the shelf break according to forecasting scenarios. The strengthened evaporation is the key process for the ECSs to get cooler under these future scenarios. This study will aid in understanding the processes related to coastal ocean warming and their relative importance.