Black carbon (BC) has recently received increasing attention due to its significant roles in regional/global carbon cycle and climate change. Emission inventories showed that China was the world’s largest BC emitter. The distinct regional characteristics of high BC emission intensity and strong influence from a combination of monsoon and large-river discharge render the broad East China Marginal Seas (ECMS), including the Bohai Sea (BS), Yellow Sea (YS), and East China Sea (ECS), important BC repositories. Therefore, investigations on BC geochemistry/sources-to-sinks processes in the ECMS will contribute considerably to the regional and even global BC cycles and budgets.Based on multimedium samplings on the atmospheric depositions, river water, seawater, and surface and core sediments, we have constrained a preliminary BC sources-to-sinks processes in the coastal ECMS. The major results are as follows: (1) The BS, YS, and ECS sediments serve as major sinks for land-based BC, with these three coastal margins having an estimated BC burying rate of ~955 Gg/yr. (2) The BC budget patterns in the BS and ECS differed significantly, with comparable contributions from atmospheric deposition and riverine discharge for the BS, but with a dominant contribution from riverine discharge (>90%) for the ECS. (3) Source apportionment showed that fossil fuels combustion was the dominant (>80%) source for sedimentary BC in the BS and YS. (4) The historical trends of BC deposition fluxes retrieved from five sediment cores in the ECMS mud areas correlated well with the economic and social development of China over the past ~150 years. Of particular note is that, with the continuous changes of climate and anthropogenic activities, in future we should pay closer attention on BC in these coastal margins.