Cities are at the forefront of climate policies. 1-6 However, urban climate policies are not implemented in a vacuum; they interact with other policy goals, such as economic competitiveness or social issues. These interactions can lead to trade-offs and implementation obstacles, or to synergies. 7,8 Little analysis investigating these interactions exists, in part because it requires a broad interdisciplinary approach. Using a novel integrated city model, we provide a first quantification of these trade-offs and synergies, going beyond the qualitative statements that have been published so far. We undertake a multicriteria analysis of three urban policies: a greenbelt policy, a zoning policy to reduce flood risk, and a transportation subsidy. Each of these policies appears to be undesirable because it has negative consequences with respect to at least one policy goal; however, in a policy mix, the consequences of each policy are not simply additive. This nonlinearity permits building policy combinations that are win-win strategies. In particular, flood zoning and greenbelt policies are unlikely to be accepted if they are not combined with transportation policies. Our results show that stand-alone adaptation and mitigation policies are unlikely to be politically acceptable and emphasize the need to mainstream climate policy within urban planning.Urban policies have multiple goals, such as enhancing the quality of life and the city's economic competitiveness by means of affordable housing and office space, amenities, and efficient public services. Urban policies also have social objectives aimed at poverty and social segregation issues, safety and security, and public health. They have environmental goals as well, such as reducing air and water pollution and preserving natural areas. In addition to this long list of goals, urban policies now face new challenges from climate change, including adaptation and mitigation needs. [1][2][3][4][5][6] Adaptation and emission reduction policies rely on the same tools, giving rise to both synergies and conflicts. 7,8 Synergies and conflicts with other policy goals also exist, and environmental policies can result in positive feedback with respect to economic and social issues. A decrease in car congestion increases residents' quality of life, enhances economic competitiveness, reduces accessibility inequalities among neighborhoods, and decreases air pollution and GHG emissions. Conversely, while enlarging parks and introducing more vegetation in cities can be a useful way to adapt cities to higher temperatures and can improve the quality of life, such actions may also reduce population density and lead to increased GHG