Coastal ecosystems are increasingly recognized as a vital nature-based climate solution due to their exceptional capacity for carbon sequestration. However, the spatial distribution and quantification of soil organic carbon accumulation rate (OCAR) at the global scale remain limited. Here, we assemble an open global dataset of soil OCAR in coastal ecosystems from a systematic literature review. The dataset has 8,998 field observations reported in 247 peer-reviewed articles, encompassing four ecosystem types (mangroves, salt marshes, seagrasses, and tidal flats) and specific measurement methods. In addition, publication details of the source articles, geographical and ecological attributes of the sampling sites, and information for each observation were included in the dataset. The dataset can be used to more accurately quantify and map global coastal soil carbon sequestration capacity, enabling the development of global spatial-temporal prediction models. This dataset serves as a vital scientific foundation for the management strategies of coastal ecosystems and future carbon credit markets.