<p>Salt marsh, mangrove, and seagrass ecosystems, collectively termed blue carbon ecosystems, play important roles in the global carbon cycle and climate change mitigation. However, the impact of sea level rise (SLR) on the carbon sequestration function of coastal wetlands remains elusive and constitutes one of the greatest challenges in blue carbon science. Therefore, in this review, we aimed to explore the mechanisms through which SLR affects sediment carbon processes, stocks, fractions, and stability in coastal wetlands. We determined that moderate rates of SLR may enhance the carbon sequestration function of these ecosystems by increasing plant productivity, promoting vertical accretion, and promoting the rate of wetland creation (i.e., migration) at the landward margin. Conversely, excessive SLR may decrease carbon sequestration through increased vegetation mortality, sediment erosion, and organic carbon mineralization. Nevertheless, SLR will likely add unpredictable uncertainties to the potential for carbon sequestration in coastal wetlands. To address the knowledge gaps in this field, future research should focus on: (1) spatiotemporal monitoring and precise quantification of SLR effects on coastal blue carbon, (2) adaptive and feedback mechanisms governing the responses of key coastal carbon processes to SLR, (3) predictive modeling of SLR-driven carbon sequestration functions, and (4) carbon-optimized SLR adaptation strategies and technologies. This review provides valuable theoretical support and scientific references for understanding blue carbon formation and mechanisms, potential changes in blue carbon function, and management of coastal wetlands under various SLR scenarios.</p>