Seaweed farming has garnered significant attention as a rapidly expanding sector with the potential to contribute to climate change mitigation, food security, and environmental sustainability. This chapter critically examines the potential of temperate seaweed farming as a solution to mitigate climate change, focusing on its capacity to reduce greenhouse gas emissions and facilitate atmospheric carbon dioxide removal (CDR). We synthesize recent evidence on carbon fluxes within seaweed farms, including emissions generated during farming operations at sea and the carbon sequestration achieved through biomass burial under farms. While seaweed farming is often considered within the ocean CDR portfolio, our analysis highlights that the net climate impacts of seaweed farming are not always positive. Emissions from farm operations can often exceed the carbon removed during farming at sea, especially in temperate seaweed farms where energy and material inputs are higher. Furthermore, current methodologies for assessing CDR capacity of seaweed farms are limited, and the contribution of seaweed farming to climate change mitigation remains small relative to protecting or restoring natural coastal ecosystems like mangroves and seagrasses. Still, it is evident that seaweed farming is one of the most sustainable production systems around, with modest carbon emissions and low environmental impacts compared to other production systems. This suggests that, although seaweed farming may not always be a carbon sink, it remains a promising avenue for climate change mitigation through net emission reductions. This net benefit will further increase where products are replaced by low-carbon seaweed alternatives and supply chains are decarbonized.