jats:titleAbstract</jats:title>jats:pCoastal land reclamation has been practiced widely to accommodate rapid urbanization. But the exploitation of coastal wetlands also imposes ecological risks and jeopardizes ecological security in many countries. The overall effects of coastal land reclamation must therefore be assessed. We developed a conceptual framework to evaluate the ecological effects of coastal land reclamation on cropland protection along three dimensions: land quantity, ecological environment, and land quality. An integrated index system was constructed accordingly and tested by using data from Cixi, a coastal city in eastern China. Our index system generated rich information to assess the impacts of reclamation on added cropland area, landscape ecological risk, and cropland soil quality. The results showed that between 1985 and 2020, a total area of 393.71 kmjats:sup2</jats:sup> of coastal wetlands were reclaimed in Cixi City, which played a crucial part in upholding the equilibrium between the land supply and demand during urbanization. However, its adverse ecological effects were also evidenced. Coastal reclamation not only increased the landscape disturbance and ecological risk but also significantly decreased the overall cropland soil quality. The city's original reclamation‐driven development strategy is unable to meet the updated requirements of “quantity‐quality‐ecological balance” for cropland protection. Our index system can help land use policymakers monitor the ecological effects of coastal reclamation. The knowledge gained will have major policy implications for the land use management that promotes sustainability in coastal regions.</jats:p>