Seaweed stands create some of the most productive habitats in the world, but their role carbon sequestration and the potential of seaweed farming activities for climate change impacts mitigation in the oceans are not well understood. It has been proven that seaweed farming at large scales can extract nitrogen coastal areas reducing eutrophication in coastal areas. However, carbon pathways are much more complex in the ocean to understand their potential role as a mitigation tool by sequestering carbon. By harvesting the biomass, the transport and process of the biomass will produce again CO2. Also, seaweeds are not trees and they will not meet the criteria for sequestering carbon for 100s of years. In addition, seaweed produce large quantities of dissolved and particulate organic matter and how matter move with the currents are complex as they may not always allow this matter to reach high depths to be considered sequestered. Finally pieces and whole plants get detached by storms and this biomass will move also into different directions. Whether the amount of Carbon sequestered is higher than the biomass decomposed in the surface producing again CO2, still requires a deeper understanding. This study analyses known and unknows of the potential mitigation of large-scale seaweed farming on climate change and discuss present limitations. Funding: ANID (CeBiB, FB-0001).