Green tides are part of the larger class of harmful algal blooms (HAB), and have developed worldwide at a high rate during the last three decades, favoured by the eutrophication of coastal waters due to human activities. The massive accumulation of seaweeds on the shore resulting from green tides generates a variety of damages to market and non-market activities, and is a potential threat to human health. This work focuses on the green tide phenomenon in the Chinese Yellow Sea, and provides an economic assessment in a cost-benefit perspective. It first investigates the bioeconomic mechanisms of these episodes, their economic consequences, public management policies, and stakeholders' perceptions. Then, it tries to quantify the social cost of green tides, including management costs and residual costs to market and non-market activities. On this basis, alternative management scenarios are compared.